Evolution of Phosphagen Kinase VII. Isolation of Glycocyamine Kinase from the Polychaete Neanthes diversicolor and the cDNA-Derived Amino Acid Sequences of α and β Chains

Glycocyamine kinase (GK) was isolated from the marine polychaete Neanthes diversicolor by gel filtration, DEAE-cellulose chromatography, butyl-Toyopearl hydrophobic chromatography, and chromatofocusing. The GK was eluted as a single peak on the latter three chromatographies, and the molecular mass for the native GK was estimated to be about 80 kDa. The SDS–PAGE showed that the isolated GK consists of two distinct subunits in equal proportion, α and β chains, with molecular masses of 42.2 and 43.8 kDa, respectively. The present results suggest that the Neanthes GK has a heterodimeric structure. The cDNAs for α and β chains of Neanthes GK were amplified by PCR and their cDNA-derived amino acid sequences were determined. The α and β chains are composed of 374 and 390 amino acids, and the molecular masses were calculated to be 42,392 and 43,966 Da, respectively, in good agreement with the apparent masses on SDS–PAGE. The β chain has a characteristic N-terminal extension of 15 amino acids, and all of the sequence differences between α and β chains were restricted in the N-terminal region of 50 residues. The overall sequence identity was 92%. The occurrence of heterodimeric nature in Neanthes GK is of great interest from the evolutionary point of view, because the heterodimeric structure is only known for creatine kinase MB-isozyme specific for mammalian heart muscle among phosphagen kinases.     

Purification and partial characterization of creatine kinase from electric organ of Electrophorus electricus (L.)

The present investigation deals with the purification and the partial characterization of the soluble creatine kinase (CK) isoenzyme, isolated from the electric organ electrocyte of Electrophorus electricus (L.). Purification was performed by precipitation of the enzyme in the crude extract with ammonium sulfate (80%). The precipitate obtained was analyzed on an ion exchange column of diethylaminoethyl cellulose-52 (DEAE) followed by gel filtration on Superose 12 in a Fast Protein Liquid Chromatography (FPLC) system. Electrophoretic mobility of the active peak confirmed previous results identifying the hybrid isoenzyme MB in the electrocyte cytoplasm. Electrocyte CK is a dimeric enzyme with two identical subunits of approximately 40 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The sequence analysis of the N-terminal peptide (14 amino acids) of the 40 kDa subunit showed homology with other CK enzymes from electric fish (Torpedo) and human muscle type CK.     

COMMD6 from amphioxus Branchiostoma belcheri (BbCOMMD6) interacts with creatine kinase and inhibits its activity

COMM domain-containing proteins are a group of recently discovered proteins; their biochemical characterization remains much limited. Here we demonstrate that a cDNA encoding Branchiostoma belcheri COMMD6, designated BbCOMMD6, codes for a protein of 203 amino acids, with a COMM domain at its C-terminal region and an extended N-terminal portion. BbCOMMD6 is mainly present in the cytosol. In contrast to COMMD1, the presence of Cu(II) cannot enhance recombinant BbCOMMD6 dimer formation. Both the pull-down and reverse pull-down assays reveal that BbCOMMD6 interacts with the creatine kinase (CK), an essential enzyme involved in energy metabolism, forming a heterodimer BbCOMMD6-CK. The enzymatic activity assays show that CK activities are inhibited by BbCOMMD6 in a dose-dependent manner. All these data suggest that BbCOMMD6 is involved in energy transduction, via binding to CK and inhibiting activities of CK, and offer first clues to its role as a regulator of CK activities.     

Role of amino-acid residue 95 in substrate specificity of phosphagen kinases

The purpose of this study is to elucidate the mechanisms of guanidine substrate specificity in phosphagen kinases, including creatine kinase (CK), glycocyamine kinase (GK), lombricine kinase (LK), taurocyamine kinase (TK) and arginine kinase (AK). Among these enzymes, LK is unique in that it shows considerable enzyme activity for taurocyamine in addition to its original target substrate, lombricine. We earlier proposed several candidate amino acids associated with guanidine substrate recognition. Here, we focus on amino-acid residue 95, which is strictly conserved in phosphagen kinases: Arg in CK, Ile in GK, Lys in LK and Tyr in AK. This residue is not directly associated with substrate binding in CK and AK crystal structures, but it is located close to the binding site of the guanidine substrate. We replaced amino acid 95 Lys in LK isolated from earthworm Eisenia foetida with two amino acids, Arg or Tyr, expressed the modified enzymes in Escherichia coli as a fusion protein with maltose-binding protein, and determined the kinetic parameters. The K95R mutant enzyme showed a stronger affinity for both lombricine (Km=0.74 mM and kcat/Km=19.34 s(-1) mM(-1)) and taurocyamine (Km=2.67 and kcat/Km=2.81), compared with those of the wild-type enzyme (Km=5.33 and kcat/Km=3.37 for lombricine, and Km=15.31 and kcat/ Km=0.48for taurocyamine). Enzyme activity of the other mutant, K95Y, was dramatically altered. The affinity for taurocyamine (Km=1.93 and kcat/Km=6.41) was enhanced remarkably and that for lombricine (Km=14.2 and kcat/Km=0.72) was largely decreased, indicating that this mutant functions as a taurocyamine kinase. This mutant also had a lower but significant enzyme activity for the substrate arginine (Km=33.28 and kcat/Km=0.01). These results suggest that Eisenia LK is an inherently flexible enzyme and that substrate specificity is strongly controlled by the amino-acid residue at position 95.     

Evidence for production of a new lantibiotic (butyrivibriocin OR79A) by the ruminal anaerobe Butyrivibrio fibrisolvens OR79: characterization of the structural gene encoding butyrivibriocin OR79A

The ruminal anaerobe Butyrivibrio fibrisolvens OR79 produces a bacteriocin-like activity demonstrating a very broad spectrum of activity. An inhibitor was isolated from spent culture fluid by a combination of ammonium sulfate and acidic precipitations, reverse-phase chromatography, and high-resolution gel filtration. N-terminal analysis of the isolated inhibitor yielded a 15-amino-acid sequence (G-N/Q-G/P-V-I-L-X-I-X-H-E-X-S-M-N). Two different amino acid residues were detected in the second and third positions from the N terminus, indicating the presence of two distinct peptides. A gene with significant homology to one combination of the determined N-terminal sequence was cloned, and expression of the gene was confirmed by Northern blotting. The gene (bvi79A) encoded a prepeptide of 47 amino acids and a mature peptide, butyrivibriocin OR79A, of 25 amino acids. Significant sequence homology was found between this peptide and previously reported lantibiotics containing the double-glycine leader peptidase processing site. Immediately downstream of bvi79A was a second, partial open reading frame encoding a peptide with significant homology to proteins which are believed to be involved in the synthesis of lanthionine residues. These findings indicate that the isolated inhibitory peptides represent new lantibiotics. Results from both total and N-terminal amino acid sequencing indicated that the second peptide was identical to butyrivibriocin OR79A except for amino acid substitutions in positions 2 and 3 of the mature lantibiotic. Only a single coding region was detected when restriction enzyme digests of total DNA were probed either with an oligonucleotide based on the 5' region of bvi79A or with degenerate oligonucleotides based on the predicted sequence of the second peptide.     

Structural and functional implications of the amino acid sequences of dimeric, cytoplasmic and octameric mitochondrial creatine kinases from a protostome invertebrate.

The cDNA and deduced amino-acid sequences for dimeric and octameric isoforms of creatine kinase (CK) from a protostome, the polychaete Chaetopterus variopedatus, were elucidated and then analysed in the context of available vertebrate CK sequences and the recently determined crystal structure of chicken sarcomeric mitochondrial CK (MiCK). As protostomes last shared a common ancestor with vertebrates roughly 700 million years ago, observed conserved residues may serve to confirm or reject contemporary hypotheses about the roles of particular amino acids in functional/structural processes such as dimer/octamer formation and membrane binding. The isolated cDNA from the dimeric CK consisted of 1463 nucleotides with an open reading frame of 1116 nucleotides encoding a 372-amino-acid protein having a calculated molecular mass of 41.85 kDa. The percentage identity of C. variopedatus dimeric CK to vertebrate CK is as high as 69%. The octameric MiCK cDNA is composed of 1703 nucleotides with an open reading frame of 1227 nucleotides. The first 102 nucleotides of the open reading frame encode a 34-amino-acid leader peptide whereas the mature protein is composed of 375 amino acids with a calculated molecular mass of 42.17 kDa. The percentage identity of C. variopedatus MiCK to vertebrate CK is as high as 71%. This similarity is also evident in residues purported to be important in the structure and function of dimeric and octameric CK: (a) presence of seven basic amino acids in the C-terminal end thought to be important in binding of MiCK to membranes; (b) presence of a lysine residue (Lys110 in chicken MiCK) also thought to be involved in membrane binding; and (c) presence of a conserved tryptophan thought to be important in dimer stabilization which is present in all dimeric and octameric guanidino kinases. However, C. variopedatus MiCK lacks the N-terminal heptapeptide present in chicken MiCK, which is thought to mediate octamer stabilization. In contrast with vertebrate MiCK, polychaete octamers are very stable indicating that dimer binding into octamers may be mediated by additional and/or other residues. Phylogenetic analyses showed that both octamer and dimer evolved very early in the CK lineage, well before the divergence of deuterostomes and protostomes. These results indicate that the octamer is a primitive feature of CK rather than being a derived and advanced character.     

Origin and properties of cytoplasmic and mitochondrial isoforms of taurocyamine kinase

Taurocyamine kinase (TK) is a member of the highly conserved family of phosphagen kinases that includes creatine kinase (CK) and arginine kinase. TK is found only in certain marine annelids. In this study we used PCR to amplify two cDNAs coding for TKs from the polychaete Arenicola brasiliensis, cloned these cDNAs into the pMAL plasmid and expressed the TKs as fusion proteins with the maltose-binding protein. These are the first TK cDNA and deduced amino acid sequences to be reported. One of the two cDNA-derived amino acid sequences of TKs shows a high amino acid identity to lombricine kinase, another phosphagen kinase unique to annelids, and appears to be a cytoplasmic isoform. The other sequence appears to be a mitochondrial isoform; it has a long N-terminal extension that was judged to be a mitochondrial targeting peptide by several on-line programs and shows a higher similarity in amino acid sequence to mitochondrial creatine kinases from both vertebrates and invertebrates. The recombinant cytoplasmic TK showed activity for the substrates taurocyamine and lombricine (9% of that of taurocyamine). However, the mitochondrial TK showed activity for taurocyamine, lombricine (30% of that of taurocyamine) and glycocyamine (7% of that of taurocyamine). Neither TK catalyzed the phosphorylation of creatine. Comparison of the deduced amino acid sequences of mitochondrial CK and TK indicated that several key residues required for CK activity are lacking in the mitochondrial TK sequence. Homology models for both cytoplasmic and mitochondrial TK, constructed using CK templates, provided some insight into the structural correlation of differences in substrate specificity between the two TKs. A phylogenetic analysis using amino acid sequences from a broad spectrum of phosphagen kinases showed that annelid-specific phosphagen kinases (lombricine kinase, glycocyamine kinase and cytoplasmic and mitochondrial TKs) are grouped in one cluster, and form a sister-group with CK sequences from vertebrate and invertebrate groups. It appears that the annelid-specific phosphagen kinases, including cytoplasmic and mitochondrial TKs, evolved from a CK-like ancestor(s) early in the divergence of the protostome metazoans. Furthermore, our results suggest that the cytoplasmic and mitochondrial isoforms of TK evolved independently.     

Cloning and sequence analysis of lily and tobacco guanylate kinases

Guanylate kinase is an essential enzyme in the nucleotide biosynthetic pathway, catalyzing the reversible transfer of the terminal phospharyl group of ATP to GMP or dGMP. This enzyme has been well studied from several organisms and many structural and functional details have been characterized. Animal GMP kinases have also been implicated in signal transduction pathways. However, the corresponding role by plant derived GMP kinases remains to be elucidated. Full-length cDNA clones encoding enzymatically active guanylate kinases were isolated from cDNA libraries of lily and tobacco. Lily cDNA is predicted to encode a 392-amino acid protein with a molecular mass of 43.1 kDa and carries amino- and carboxy- terminal extensions of the guanylate kinase (GK)-like domain. But tobacco cDNA is predicted to encode a smaller protein of 297-amino acids with a molecular mass of 32.7 kDa. The amino acid residues known to participate in the catalytic activity of functionally characterized GMP kinases, are also conserved in GK domains of LGK-1 and NGK-1. The GK domains of NGK-1, LGK-1 and previously characterized AGK-1 from Arabidopsis exhibit 74–84% identity, whereas their N- and C-terminal domains are more divergent with amino acid conservation in the order of 48-55%. Phylogenetic analysis on the deduced amino acid sequences reveals that NGK-1 and LGK-1 form one distinct subgroup along with AGK-1 and AGK-2 homologues from Arabidopsis. Isolation of GMP kinases from diverse plant species like lily and tobacco adds a new dimension in understanding their role in cell signaling pathways that are associated with plant growth and development.     

Isolation and characterization of the gene and cDNA encoding human mitochondrial creatine kinase

Creatine kinase (CK; EC 2.7.3.2) isoenzymes play prominent roles in energy metabolism. Nuclear genes encode three known CK subunits: cytoplasmic muscle (MCK), cytoplasmic brain (BCK), and mitochondrial (MtCK). We have isolated the gene and cDNA encoding human placental MtCK. By using a dog heart MCK cDNA-derived probe, the 7.0-kb EcoRI fragment from one cross-hybridizing genomic clone was isolated and its complete nucleotide sequence determined. A region of this clone encoded predicted amino acid sequence identical to residues 15-26 of the human heart MtCK NH2-terminal protein sequence. The human placental MtCK cDNA was isolated by hybridization to a genomic fragment encoding this region. The human placental MtCK gene contains 9 exons encoding 416 amino acids, including a 38-amino acid transit peptide, presumably essential for mitochondrial import. Residues 1-14 of human placental MtCK cDNA-derived NH2-terminal sequence differ from the human heart MtCK protein sequence, suggesting that tissue-specific MtCK mRNAs are derived from multiple MtCK genes. RNA blot analysis demonstrated abundant MtCK mRNA in adult human ventricle and skeletal muscle, low amounts in placenta and small intestine, and a dramatic increase during in vitro differentiation induced by serum-deprivation in the non-fusing mouse smooth muscle cell line, BC3H1. These findings demonstrate coordinate regulation of MtCK and cytosolic CK gene expression and support the phosphocreatine shuttle hypothesis.     

Human arylsulfatase B: MOPAC cloning, nucleotide sequence of a full-length cDNA, and regions of amino acid identity with arylsulfatases A and C

cDNAs encoding the human lysosomal hydrolase, arylsulfatase B (ASB; N-acetylgalactosamine-4-sulfatase, EC 3.1.6.1), were isolated from a hepatoma cell cDNA library using an ASB-specific oligonucleotide generated by the MOPAC (mixed oligonucleotide primed amplification of cDNA) technique. To facilitate cDNA cloning, human ASB was purified to apparent homogeneity and a total of 112 amino acid residues were microsequenced from the N-terminus and four internal tryptic peptides of the 47-kDa subunit. Based on the ASB N-terminal amino acid sequence, two oligonucleotide mixtures containing inosines to reduce the mixture complexity were constructed and used as primers to amplify an ASB-specific product from human placental cDNA by the polymerase chain reaction. DNA sequencing of this MOPAC product demonstrated colinearity with 21 N-terminal ASB amino acids. Based on this sequence and on codon usage for the adjacent conserved amino acids in human arylsulfatases A and C, a unique 66-mer was synthesized and used to screen a human hepatoma cell cDNA library. Four putative positive cDNA clones were isolated, and the largest insert (pASB-1) was sequenced in both orientations. The 1834-bp pASB-1 insert had a 1278-bp open reading frame encoding 425 amino acids that was colinear with 85 microsequenced amino acids of the purified enzyme, demonstrating its authenticity. Using the pASB-1 cDNA as a probe, a full-length cDNA clone, pASB-4, was isolated from a human testes library and sequenced in both orientations. pASB-4 had a 2811-bp insert containing a 559-bp 5' untranslated sequence, a 1602-bp open reading frame encoding 533 amino acids (six potential N-glycosylation sites), a 641-bp 3' untranslated sequence, and a 9-bp poly(A) tract. Comparison of the predicted amino acid sequences of arylsulfatases A, B, and C revealed regions of identity, particularly in their N-termini.     

Isolation, characterization and cDNA cloning of a one-lobed transferrin from the ascidian Halocynthia roretzi

Transferrin was isolated from plasma of the ascidian Halocynthia roretzi by ion-exchange chromatography. The molecular weight of the plasma transferrin was determined to be 52K by SDS-polyacrylamide gel electrophoresis and gel filtration. Ascidian plasma transferrin was found to bind one mole of iron ion per mole of protein. The reductive S-pyridylethylated transferrin was subjected to Edman degradation analysis for determination of the N-terminal amino acid sequence, and it was also subjected to proteolytic fragmentation to yield peptide fragments, whose amino acid sequences were determined by Edman degradation analysis. Using the above amino acid sequences, a cDNA clone (1880 base pairs) encoding a protein of 372 amino acids containing a signal peptide of 21 amino acids was isolated from an H. roretzi hepatopancreas cDNA library. The reduced amino acid sequence contains the same sequences of the peptide fragments. A comparison of the amino acid sequence of ascidian transferrin with those of other members of the transferrin family revealed that the ascidian transferrin is composed of only the N-terminal lobe of two-lobed vertebrate transferrins. Thus, a one-lobed transferrin is present in the ascidian H. roretzi.     

Isolation, amino acid analysis and N-terminal sequence determination of the two subunits of the nickel-containing hydrogenase of Desulfovibrio gigas

The two subunits of the nickel-iron hydrogenase from Desulfovibrio gigas have been purified by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis and their amino acid compositions have been determined. The N-terminal sequences for 15 residues of the large subunit (Mr 62,000) and 25 residues of the small subunit (Mr 26,000), respectively, were established. The occurrence of several cysteine residues in the small subunit is discussed in relation with their possible role in the binding of the redox centers of the enzyme.     

Evidence for Production of a New Lantibiotic (Butyrivibriocin OR79A) by the Ruminal Anaerobe Butyrivibrio fibrisolvens OR79: Characterization of the Structural Gene Encoding Butyrivibriocin OR79A

The ruminal anaerobe Butyrivibrio fibrisolvens OR79 produces a bacteriocin-like activity demonstrating a very broad spectrum of activity. An inhibitor was isolated from spent culture fluid by a combination of ammonium sulfate and acidic precipitations, reverse-phase chromatography, and high-resolution gel filtration. N-terminal analysis of the isolated inhibitor yielded a 15-amino-acid sequence (G-N/Q-G/P-V-I-L-X-I-X-H-E-X-S-M-N). Two different amino acid residues were detected in the second and third positions from the N terminus, indicating the presence of two distinct peptides. A gene with significant homology to one combination of the determined N-terminal sequence was cloned, and expression of the gene was confirmed by Northern blotting. The gene (bvi79A) encoded a prepeptide of 47 amino acids and a mature peptide, butyrivibriocin OR79A, of 25 amino acids. Significant sequence homology was found between this peptide and previously reported lantibiotics containing the double-glycine leader peptidase processing site. Immediately downstream of bvi79A was a second, partial open reading frame encoding a peptide with significant homology to proteins which are believed to be involved in the synthesis of lanthionine residues. These findings indicate that the isolated inhibitory peptides represent new lantibiotics. Results from both total and N-terminal amino acid sequencing indicated that the second peptide was identical to butyrivibriocin OR79A except for amino acid substitutions in positions 2 and 3 of the mature lantibiotic. Only a single coding region was detected when restriction enzyme digests of total DNA were probed either with an oligonucleotide based on the 5′ region of bvi79A or with degenerate oligonucleotides based on the predicted sequence of the second peptide.     

Cloning of deoxynucleoside monophosphate kinase genes and biosynthesis of deoxynucleoside diphosphates

The genes encoding four deoxynucleoside monophosphate kinase (dNMP kinase) enzymes, including ADK1 for deoxyadenylate monophosphate kinase (AK), GUK1 for deoxyguanylate monophosphate kinase (GK), URA6 for deoxycytidylate monophosphate kinase (CK), and CDC8 for deoxythymidylate monophosphate kinase (TK), were isolated from the genome of Saccharomyces cerevisiae ATCC 2610 strain and cloned into E. coli strain BL21(DE3). Four recombinant plasmids, pET17b-JB1 containing ADK1, pET17b-JB2 containing GUK1, pET17b-JB3 containing URA6, and pET17b-JB4 containing CDC8, were constructed and transformed into E. coli strain for over-expression of AK, GK, CK, and TK. The amino acid sequences of these enzymes were analyzed and a putative conserved peptide sequence for the ATP active site was proposed. The four deoxynucleoside diphosphates (dNDP) including deoxyadenosine diphosphate (dADP), deoxyguanosine diphosphate (dGDP), deoxycytidine diphosphate (dCDP), and deoxythymidine diphosphate (dTDP), were synthesized from the corresponding deoxynucleoside monophosphates (dNMP) using the purified AK, GK, CK, and TK, respectively. The effects of pH and magnesium ion concentration on the dNDP biosynthesis were found to be important. A kinetic model for the synthetic reactions of dNDP was developed based on the Bi-Bi random rapid equilibrium mechanism. The kinetic parameters including the maximum reaction velocity and Michaelis-Menten constants were experimentally determined. The study on dNDP biosynthesis reported in this article are important to the proposed bioprocess for production of deoxynucleoside triphosphates (dNTP) that are used as precursors for in vitro DNA synthesis. There is a significant advantage of using enzymatic biosyntheses of dNDP as compared to the chemical method that has been in commercial use.     

Purification,Characterization, and Molecular Cloning of a Thermostable Superoxide Dismutase from Thermoascus aurantiacus

A thermostable superoxide dismutase [(SOD) EC 1.15.1.1] from a Thermoascus aurantiacus var. levisporus was purified to sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) homogeneity by a series of column chromatographies. The molecular mass of a single band of the enzyme was estimated to be 16.8 kDa by SDS–PAGE. The molecular mass was estimated to be 33.2 kDa by gel filtration on Sephacryl S-100, indicating that the enzyme was composed of two identical subunits of 16.8 kDa each. N-terminal amino acid sequencing (seven residues) yielded VKAVAVL. Using RACE-PCR, a Cu, Zn-SOD gene was cloned from T. aurantiacus var. levisporus. The sequence was 705 bp and contained a 468 bp ORF encoding a Cu, Zn-SOD of 155 amino acid residues.     

Characterization of the pcp gene of Pseudomonas fluorescens and of its product, pyrrolidone carboxyl peptidase (Pcp).

The gene pcp, encoding pyrrolidone carboxyl peptidase (Pcp), from Pseudomonas fluorescens MFO was cloned and its nucleotide sequence was determined. This sequence contains a unique open reading frame (pcp) coding for a polypeptide of 213 amino acids (M(r) 22,441) which has significant homology to the Pcps from Streptococcus pyogenes, Bacillus subtilis, and Bacillus amyloliquefaciens. Comparison of the four Pcp sequences revealed two highly conserved motifs which may be involved in the active site of these enzymes. The cloned Pcp from P. fluorescens was purified to homogeneity and appears to exist as a dimer. This enzyme displays a Michaelis constant of 0.21 mM with L-pyroglutamyl-beta-naphthylamide as the substrate and an absolute substrate specificity towards N-terminal pyroglutamyl residues. Studies of inhibition by chemical compounds revealed that the cysteine and histidine residues are essential for enzyme activity. From their conservation in the four enzyme sequences, the Cys-144 and His-166 amino acids are proposed to form a part of the active site of these enzymes.     

NADP-dependent isocitrate dehydrogenase from the halophilic archaeon Haloferax volcanii: cloning,sequence determination and overexpression in Escherichia coli

A gene encoding NADP-dependent Ds-threo-isocitrate dehydrogenase was isolated from Haloferax volcanii genomic DNA by using a combination of polymerase chain reaction and screening of a lambda EMBL3 library. Analysis of the nucleotide sequence revealed an open reading frame of 1260 bp encoding a protein of 419 amino acids with 45837 Da molecular mass. This sequence is highly similar to previously sequenced isocitrate dehydrogenases. In the alignment of the amino acid sequences with those from several archaeal and mesophilic NADP-dependent isocitrate dehydrogenases, the residues involved in dinucleotide binding and isocitrate binding are well conserved. We have developed methods for the expression in Escherichia coli and purification of the enzyme from H. volcanii. This expression was carried out in E. coli as inclusion bodies using the cytoplasmic expression vector pET3a. The enzyme was refolded by solubilisation in 8 M urea followed by dilution into a buffer containing EDTA, MgCl(2) and 3 M NaCl. Maximal activity was obtained after several hours incubation at room temperature.     

Phenol hydroxylase from Trichosporon cutaneum: gene cloning, sequence analysis, and functional expression in Escherichia coli.

A cDNA clone encoding phenol hydroxylase from the soil yeast Trichosporon cutaneum was isolated and characterized. The clone was identified by hybridization screening of a bacteriophage lambda ZAP-based cDNA library with an oligonucleotide probe which corresponded to the N-terminal amino acid sequence of the purified enzyme. The cDNA encodes a protein consisting of 664 amino acids. Amino acid sequences of a number of peptides obtained by Edman degradation of various cleavage products of the purified enzyme were identified in the cDNA-derived sequence. The phenol hydroxylase cDNA was expressed in Escherichia coli to yield high levels of active enzyme. The E. coli-derived phenol hydroxylase is very similar to the T. cutaneum enzyme with respect to the range of substrates acted upon, inhibition by excess phenol, and the order of magnitude of kinetic parameters in the overall reaction. Southern blot analysis revealed the presence of phenol hydroxylase gene-related sequences in a number of T. cutaneum and Trichosporon beigelii strains and in Cryptococcus elinovii but not in Trichosporon pullulans, Trichosporon penicillatum, or Candida tropicalis.     

Highly thermostable and surfactant-activated chitinase from a subseafloor bacterium,Laceyella putida

A novel chitinase (LpChiA) was purified to homogeneity from a culture of Laceyella putida JAM FM3001. LpChiA hydrolyzed colloidal chitin optimally at a pH of 4 in an acetate buffer and temperature of 75?ºC. The enzyme was remarkably stable to incubation at 70?ºC up to 1 h at pH 5.2, and its activity half-life was 3 days. The molecular mass of the enzyme was around 38 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and around 75 kDa by gel filtration, suggesting it is a homodimer. The enzyme activity was enhanced about 60 % when pre-incubated with anionic, cationic, and nonionic surfactants. The gene for LpChiA was cloned by PCR and sequenced. The nucleotide sequence of the gene consisted of 1,683 bp encoding 560 amino acids. The N-terminal and internal amino acid sequences of the purified LpChiA from L. putida suggested that the mature enzyme was composed of 384 amino acids after cleaving its 176 N-terminal amino acids and dimerized to express its activity. The deduced amino acid sequence of the mature enzyme showed the highest similarity to chitinase of Laceyella sacchari with 79 % identity.     

Primary structure of human carcinoembryonic antigen (CEA) deduced from cDNA sequence

The cDNAs corresponding to the mRNA encoding a polypeptide which is immunoreactive with the antisera specific to carcinoembryonic antigen (CEA) (1) are cloned. The amino acid sequences deduced from the nucleotide sequences of the cDNAs show that it is synthesized as a precursor with a signal peptide followed by 668 amino acids of the putative mature CEA peptide, whose N-terminal 24 amino acids and amino acids 286 to 295 exactly coincide with those known for N-terminal sequences of CEA (2) and NFA-1 (3), respectively. The first 108 N-terminal residues are followed by three very homologous repetitive domains of 178 residues each and then by 26 mostly hydrophobic residues which probably comprise a membrane anchor. Each repetitive domains contains 4 cysteines at precisely the same positions and as many as 28 possible N-glycosylation sites are found in the CEA peptide region agreeing with high carbohydrate content of purified CEA.