Maize Glutamine Synthetase Cdnas: Isolation by Direct Genetic Selection in Escherichia Coli

Maize glutamine synthetase cDNA clones were isolated by genetic selection for functional rescue of an Escherichia coli delta glnA mutant growing on medium lacking glutamine. The Black Mexican Sweet cDNA library used in this study was constructed in pUC13 such that cDNA sense strands were transcribed under the control of the lac promoter. E. coli delta glnA cells were transformed with cDNA library plasmid DNA, grown briefly in rich medium to allow phenotypic expression of the cDNAs and the pUC13 ampr gene, and challenged to grow on agar medium lacking glutamine. Large numbers of glutamine synthetase cDNA clones have been identified in individual 150-mm Petri dishes; all characterized cDNA clones carry complete coding sequences. Two cDNAs identical except for different 5' and 3' termini have been sequenced. The major open reading frame predicts a protein with an amino acid sequence that exhibits striking similarity to the amino acid sequences of the predicted products of previously sequenced eukaryotic glutamine synthetase cDNAs and genes. In addition, the maize glutamine synthetase cDNAs were shown to contain a 5' mini-ORF of 29 codons separated by 37 nucleotide pairs from the major ORF. This mini-ORF was shown not to be essential for the functional rescue of the E. coli delta glnA mutant. Expression of the cDNAs in E. coli is presumed to be due to the function of a polycistronic hybrid lac messenger RNA or translational fusions encoded by the pUC plasmids. Proteins of the expected sizes encoded by two different pUC clones were shown to react with antibodies to tobacco glutamine synthetase.     

Cloning and expression of cynomolgus monkey and baboon zona pellucida proteins

Partial clones for the three cynomolgus monkey (Macaca fasicularis) zona pellucida genes (cmZPA, cmZPB, and cmZPC) have previously been isolated. These partial clones contained the sequences for the C-terminal portion of each rcmZP protein. To obtain full-length clones for each cmZP, a fresh cynomolgus monkey ovarian cDNA library was constructed. PCR methodology was employed to speed the isolation of full-length clones for each cmZP cDNA. The 3' primers were designed based on sequence information from the previously identified clones; the 5' primers were designed using the human ZP sequences. The PCR technique yielded full-length clones of cmZPA and cmZPC, but not of cmZPB. Therefore, a genomic clone of cmZPB was isolated and the sequence determined. The exon/intron structure is nearly identical to the human ZPB exon/intron structure. New PCR primers were designed based on the cynomolgus monkey ZPB genomic sequence, and a full-length cmZPB cDNA was obtained. The same primers that were used to generate the cmZPB were also used to generate a baboon (Papio cynocephalus) ZPB (bZPB) cDNA. As was done previously for the human zona pellucida (hZP) cDNAs, the cmZP, and bZPB cDNAs were transferred to shuttle vectors for transfection into Chinese Hamster Ovary (CHO) cells. Stable cell lines for producing each ZP protein were isolated. Each cell line secreted the desired recombinant zona pellucida (rZP) protein into the culture medium, and each protein was purified using an established protocol. In terms of size and purity, the purified recombinant cmZP (rcmZP) and rbZPB proteins resemble the rhZP proteins.     

Characterization and cloning of chitin deacetylases from Rhizopus circinans

Chitin deacetylase catalyzes hydrolysis of the acetamido groups of N-acetylglucosamine of chitin in fungal cell walls. Here a chitin deacetylase secreted by Rhizopus circinans was purified to homogeneity and partially characterized. The enzyme exhibits an apparent molecular weight of approximately 75kDa. At 37 degrees C it shows optimal activity at pH 5.5-6. Its pH stability and thermal stability are good. Mn(2+) and Mg(2+) slightly enhance the activity of the enzyme and Cu(2+) strongly inhibits it. An R. circinans cDNA library was constructed and screened with a homologous probe synthesized by RT-PCR or with synthetic primers derived from the N-terminal amino-acid sequence of the native purified chitin deacetylase. Three chitin deacetylase cDNAs (RC, D2, and I3/2) were isolated from the cDNA library and sequenced. These cDNAs exhibit features characteristic of chitin deacetylase sequences: the presence of a polysaccharide deacetylase domain, a metal-binding triad, the conserved catalytic residues, and high homology with various chitin deacetylase genes. The cDNAs were cloned in a Pichia pastoris expression system and produced as polyhistidine-tagged proteins. Only one recombinant enzyme (called RC) was active under the tested conditions. It was purified to homogeneity in a single step and further characterized. The protein showed an apparent molecular mass of approximately 75kDa and, like the native enzyme, showed optimal activity at pH 5.5-6 at 37 degrees C. It was strongly inhibited by Cu(2+). The isolation of several chitin deacetylase cDNAs from the same microorganism is discussed.     

Mammalian protein serine/threonine phosphatase 2C: cDNA cloning and comparative analysis of amino acid sequences.

Complementary DNA encoding rat protein phosphatase 2C alpha was obtained from a liver library and used to isolate the homologous cDNAs from rabbit liver and human teratocarcinoma libraries. The amino acid sequences of the three enzymes deduced from the cDNA (382 amino acids) were extremely similar (greater than 99% identity), the maximum number of differences (between rat and human) being four. Amino acid sequences of peptides corresponding to 238 residues (61%) of the protein phosphatase 2C beta isoform from rabbit skeletal muscle were determined and showed 12 differences from the recently published sequence of the rat liver enzyme deduced from the cDNA (95% identity).     

Molecular cloning and characterization of three distinct choriogenins in masu salmon, Oncorhynchus masou

Three cDNAs, each encoding a different choriogenin (Chg), were isolated from a female masu salmon (Oncorhynchus masou) liver cDNA library. Two of the cDNA clones, Chg Halpha and Chg Hbeta, showed a close relationship and contained the typical domains of zona pellucida (ZP) B genes in fish, namely proline and glutamine rich repeats, a trefoil factor family domain, and a ZP domain. Specific antibodies against recombinant Chg H products (rmHalpha and rmHbeta) were generated to elucidate the relationship between the Chg H cDNAs and two types of serum Chg H protein, which were previously purified and characterized, and designated as very-high-molecular-weight vitelline envelope-related protein (vhVERP) and Chg H of masu salmon. The immunobiochemical analyses revealed that the Chg Halpha and Chg Hbeta clones encoded vhVERP and Chg H proteins, respectively. The third cDNA clone (Chg L) appeared to be a ZPC gene and, by mapping the N-terminal sequence of purified Chg L, was shown to encode serum Chg L protein. Various types of heteromultimer of the three Chgs were identified immunologically as high molecular weight chorion components, indicating the involvement of complex heterodimerization of multiple Chgs in the construction of chorion architecture in masu salmon.     

Cloning and expression of three rabbit kidney cDNAs encoding lauric acid omega-hydroxylases

cDNAs encoding three cytochrome P-450 enzymes were cloned from a rabbit kidney cDNA library. These three cDNAs exhibit greater than 90% nucleotide sequence identity across the coding region. This degree of sequence identity is also seen with P450IVA4, an enzyme that catalyzes the omega-hydroxylation of prostaglandins and that is elevated during pregnancy and induced by progesterone in rabbit lung. The 3' untranslated regions of the three cDNAs display very little sequence identity, suggesting that they are the products of distinct genes. The predicted amino acid sequences derived from each cDNA and for P450IVA4 exhibit about 85% identity. Each cDNA was inserted into an expression vector for transient transfection of COS-1 cells. The transfected cells each expressed a protein recognized by antibodies to P450IVA4. Microsomes isolated from the cells transfected with each cDNA efficiently catalyzed the omega-hydroxylation of lauric acid with rates that greatly exceed that catalyzed by microsomes isolated from the host cell line. One of the cDNAs encodes an enzyme that omega-hydroxylates prostaglandin A1; however, the specific activity was 2 orders of magnitude lower than that for lauric acid. Our results indicate that the substrate selectivity of the kidney P-450s encoded by these cDNAs is distinct from that of the lung P450IVA4 and that multiple enzymes comprise P-450 class IVA in the rabbit.     

Cloning and characterization of the cDNA encoding human adenylosuccinate synthetase.

Adenylosuccinate synthetase (AS) catalyzes the first committed step in the conversion of IMP to AMP. A cDNA was isolated from a human liver library which encodes a protein of 455 amino acids (M(r) of 49,925). Alignments of human, mouse, Dictyostelium discoideum and E. coli AS sequences identify a number of invariant residues which are likely to be important for structure and/or catalysis. The human AS sequence was also 19% identical to the human urea cycle enzyme, argininosuccinate synthetase (ASS), which catalyzes a chemically similar reaction. Both human liver and HeLa AS mRNA showed signals of 2.3 and 2.8 kb. An unmodified N-terminus is required for function of the human AS enzyme in E. coli mutants lacking the bacterial enzyme. The human cDNA provides a means to assess the possible role of AS abnormalities in unclassified, idiopathic cases of gout.     

Isolation of two genomic sequences encoding the Mr = 14,000 subunit of rat prostatein

Complementary DNAs to rat ventral prostate poly(A) RNA were cloned into pBR322 by the "dG-dC tailing" procedure. Clones containing cDNAs to the mRNAs coding for each of the three subunits of a major secretory protein (prostatein) were identified by hybrid-arrested translation. A 457-nucleotide base pair cDNA (E45) and a portion of a 365-base pair cDNA (E85) were analyzed to determine the composite complete DNA coding sequence for the Mr = 14,000 (C3) subunit of prostatein. A sequence of 12-nucleotide bases (TTTGCTGCTATG) in the signal peptide of C3 was noted to be homologous to signal peptide nucleotide sequences reported in cDNAs coding for the other two prostatein subunits, Mr = 6,000 (C1) and 10,000 (C2). Complementary DNA coding for the C3 subunit was used as a hybridization probe to screen an EcoRI rat genomic DNA library. Two unique 12-kilobase genomic clones, each containing mRNA coding sequences within 2.5-3-kilobase fragments, were identified by restriction enzyme mapping and Southern blot analysis. Restriction enzyme sites within the coding regions of both genes were analogous to the cDNA. Differences in restriction enzyme sites in regions of intervening sequences and flanking DNA established the uniqueness of the two genes. It is suggested that both genes may be transcribed in vivo.     

Expression and characterization of calmodulin-dependent protein kinase II from cloned cDNAs in Chinese hamster ovary cells

cDNAs containing the entire coding regions of the alpha and beta subunits of calmodulin-dependent protein kinase II (CaM kinase II) were isolated from a rat cerebrum cDNA library, ligated into an expression vector under the control of SV40 early promoter and introduced into Chinese hamster ovary (CHO) cells. To investigate the role of the alpha and beta subunits and their functional domains in CaM kinase II activity, the properties of the kinases expressed in the transfected cells were studied. CaM kinase II activity was detected in the transfected cells when the alpha and beta cDNAs were introduced into CHO cells simultaneously. RNA transfer blot and protein immunoblot analyses demonstrated the expression of the mRNAs and proteins of both alpha and beta subunits in the cloned cells. When alpha or beta cDNA was introduced into CHO cells separately, a significant level of the enzyme activity was also expressed, indicating that the alpha and beta subunits exhibited enzyme activity individually. The apparent Km values for ATP and MAP 2 were almost the same for the alpha subunit, beta subunit, alpha beta complex, and brain CaM kinase II. However, there was a slight difference in the affinity for calmodulin between the expressed proteins. The alpha and beta subunits expressed in the same cells polymerized to form alpha beta complex of a size similar to that of brain CaM kinase II. The alpha subunit also polymerized to form an oligomer, which showed almost the same S value as that of alpha beta complex and brain CaM kinase II. In contrast, the beta subunit did not polymerize. The alpha subunit, beta subunit, alpha beta complex, and brain CaM kinase II were autophosphorylated with [gamma-32P]ATP in the presence of Ca2+ and calmodulin, which resulted in the appearance of Ca2+-independent activity. The Ca2+-independent activity was 60-75% of the total activity as measured in the presence of Ca2+ plus calmodulin. To examine the functional relationship of peptide domains of the subunits of CaM kinase II, deleted cDNAs were introduced into CHO cells and the properties of the expressed proteins were studied. In cells transfected with alpha or beta cDNA from which the association domain was deleted, a significant level of kinase activity was expressed. However, the expressed proteins showed hardly any autophosphorylation and the appearance of Ca2+-independent enzyme activity was very low, indicating that the association domain was essential for the autophosphorylation and for the appearance of the Ca2+-independent activity.     

Cloning and expression of avian glutamine phosphoribosylpyrophosphate amidotransferase. Conservation of a bacterial propeptide sequence supports a role for posttranslational processing

The cDNA for glutamine phosphoribosylpyrophosphate amidotransferase, the regulatory enzyme of de novo purine nucleotide biosynthesis, has been cloned for the first time from an animal. The derived amino acid sequence of the avian amidotransferase is homologous with amidotransferase sequences from bacteria and yeast. An 11-amino acid propeptide in Bacillus subtilis amidotransferase is conserved in the avian enzyme. Expression in Chinese hamster ovary (CHO) cells and Escherichia coli provides evidence for two post-translational maturation steps needed for synthesis of active enzyme: incorporation of an iron component and processing of the 11-amino acid propeptide. Functional complementation of a CHO amidotransferase mutant suggests that both maturation steps take place in CHO cells. In contrast, function in E. coli requires deletion of the sequence encoding the propeptide. Defective assembly of the iron component may restrict propeptide removal and activation of the avian amidotransferase in E. coli.     

Cloning and expression of a novel variant of human interferon-gamma cDNA

A cDNA library was prepared from the poly(A) mRNA isolated from human peripheral blood lymphocytes which were induced by combined treatment with phytohemagglutinin and a phorbol ester. Recombinant plasmids containing human interferon-gamma (HuIFN-gamma) cDNAs were identified by the oligonucleotide-hybridization method. Nucleotide sequence analysis showed that the nucleotide and amino-acid sequences of HuIFN-gamma cDNA in plasmid pIFN gamma-G4 differed from the published data at amino acid position 9 (CAA for glutamine versus AAA for lysine). The cDNA in plasmid pIFN gamma-G4 was expressed under control of the simian virus 40 early promoter in monkey COS cells and a biologically active HuIFN-gamma was secreted from the cells. The cDNA was also inserted into an expression vector carrying an E. coli tryptophan promoter and was expressed in E. coli. The results suggest that the conversion from lysine to glutamine at amino acid position 9 might not affect the specific activity of HuIFN-gamma.     

Dark-induced and organ-specific expression of two asparagine synthetase genes in Pisum sativum.

Nucleotide sequence analysis of cDNAs for asparagine synthetase (AS) of Pisum sativum has uncovered two distinct AS mRNAs (AS1 and AS2) encoding polypeptides that are highly homologous to the human AS enzyme. The amino-terminal residues of both AS1 and AS2 polypeptides are identical to the glutamine-binding domain of the human AS enzyme, indicating that the full-length AS1 and AS2 cDNAs encode glutamine-dependent AS enzymes. Analysis of nuclear DNA shows that AS1 and AS2 are each encoded by single genes in P.sativum. Gene-specific Northern blot analysis reveals that dark treatment induces high-level accumulation of AS1 mRNA in leaves, while light treatment represses this effect as much as 30-fold. Moreover, the dark-induced accumulation of AS1 mRNA was shown to be a phytochrome-mediated response. Both AS1 and AS2 mRNAs also accumulate to high levels in cotyledons of germinating seedlings and in nitrogen-fixing root nodules. These patterns of AS gene expression correlate well with the physiological role of asparagine as a nitrogen transport amino acid during plant development.     

Formylglycinamide ribonucleotide synthetase from Escherichia coli: cloning, sequencing, overproduction, isolation, and characterization

The purL gene of Escherichia coli encoding the enzyme formylglycinamidine ribonucleotide (FGAM) synthetase which catalyzes the conversion of formylglycinamide ribonucleotide (FGAR), glutamine, and MgATP to FGAM, glutamate, ADP, and Pi has been cloned and sequenced. The mature protein, as deduced by the structural gene sequence, contains 1628 amino acids and has a calculated Mr of 141,418. Comparison of the purL control region to other pur loci control regions reveals a common region of dyad symmetry which may be the binding site for the "putative" repressor protein. Construction of an overproducing strain permitted purification of the protein to homogeneity. N-Terminal sequence analysis and comparison of glutamine binding domain sequences (Ebbole & Zalkin, 1987) confirm the amino acid sequence deduced from the gene sequence. The purified protein exhibits glutaminase activity of 0.02% the normal turnover, and NH3 can replace glutamine as a nitrogen donor with a Km = 1 M and a turnover of 3 min-1 (2% glutamine turnover). The enzyme forms an isolable (1:1) complex with glutamine: t1/2 is 22 min at 4 degrees C. This isolated complex is not chemically competent to complete turnover when FGAR and ATP are added, demonstrating that ammonia and glutamine are not covalently bound as a thiohemiaminal available to complete the chemical conversion to FGAM. hydroxylamine trapping experiments indicate that glutamine is bound covalently to the enzyme as a thiol ester. Initial velocity and dead-end inhibition kinetic studies on FGAM synthetase are most consistent with a sequential mechanism in which glutamine binds followed by rapid equilibrium binding of MgATP and then FGAR. Incubation of [18O]FGAR with enzyme, ATP, and glutamine results in quantitative transfer of the 18O to Pi.     

Cloning and sequencing of cDNAs coding for the human intra-acrosomal antigen SP-10.

cDNAs coding for the intra-acrosomal protein SP-10 were cloned and characterized as a first step in understanding the expression of this antigen during spermatogenesis. Three overlapping SP-10-specific cDNAs were isolated from a human testes cDNA expression library. These cDNAs hybridized to a 1.35-kb mRNA that was present in human testes but was not found in liver or placenta. Complete sequencing of these cDNAs, designated SP-10-5, SP-10-8, and SP-10-10, produced an 1117-bp sequence containing a 265-amino acid-coding region for the SP-10 protein. Hydrophobicity plots generated from the deduced amino acid sequence showed a very hydrophobic amino terminus characteristic of a signal peptide. Sequence data showed that three different amino acid repeats occurred a total of 16 times in the central third of the SP-10 protein. Interestingly, cDNA SP-10-10 has an internal 57-base pair (19 amino acids) in-frame deletion that is not present in SP-10-5, suggesting that alternative splicing generates more than one SP-10 mRNA. The SP-10 protein appears to be a unique acrosomal protein, based on previous immunohistological data and the observation that SP-10 cDNA sequences did not show any significant homology to other sequences found in the Genbank, National Biomedical Research Foundation, or Swiss sequence banks. A recombinant SP-10 fusion protein was produced in an Escherichia coli expression vector and used to generate a polyclonal antiserum. This antiserum stained the acrosomal cap in situ and reacted with a similar set of peptides on Western blots as did a monoclonal antibody to SP-10.     

Identification and characterization of cDNA clones encoding hydroxycinnamoyl-CoA:tyramine N-hydroxycinnamoyltransferase from tobacco.

The sequences of three cDNA clones that include the complete coding region of hydroxycinnamoyl-CoA:tyramine N-hydroxycinnamoyltransferase (THT) from tobacco are reported. The three cDNAs were isolated by antibody screening of a cDNA expression library produced from poly(A)+RNA purified from tobacco leaves (Nicotiana tabacum cv. Bottom Special), previously infiltrated with an incompatible strain of Ralstonia solanacearum. The identity of these clones was confirmed by the detection of THT activity in extracts of transformed Escherichia coli and by matching the translated polypeptides with tryptic enzyme sequences. cDNA clones tht4 and tht11 differ only by their 5' leader and 3' UTRs and therefore encode the same protein, whereas tht10 and tht11 exhibit 95 and 99% sequence identity at the DNA and deduced amino acid levels, respectively. The three clones encode proteins of 226 amino acids with calculated molecular masses of 26 kDa. The deduced amino acid sequences show no similarity with the sequence of anthranilate hydroxycinnamoyl/benzoyltransferase from Dianthus caryophyllus, the only enzyme exhibiting hydroxycinnamoyltransferase activity to be cloned so far in plants. In contrast, comparison of the THT amino acid sequence with protein sequence databases revealed substantial homology with mammalian diamine acetyltransferases. The THT clones hybridized to a 0.95-kb mRNA from elicited tobacco cell-suspension cultures and also to a mRNA of similar size from wound-healing potato tubers. The messengers for THT were also found to be expressed at relatively high levels in tobacco root tissues. Southern hybridization of tobacco genomic DNA with THT cDNA suggests that several copies of the THT gene occur in the tobacco genome. Inhibition experiments using amino-acid-specific reagents demonstrated that both histidyl and cysteyl residues are required for THT activity. In the course of these experiments THT was also found to be inhibited by (2-hydroxyphenyl) amino sulfinyl acetic acid 1,1-dimethylethyl ester, an irreversible inhibitor of cinnamyl alcohol dehydrogenase.     

Structure of the precursor to an enzyme mediating COOH-terminal amidation in peptide biosynthesis

Many bioactive peptides terminate with an amino acid alpha-amide at their COOH terminus. The enzyme responsible for this essential posttranslational modification is known as peptidyl-glycine alpha-amidating monooxygenase or PAM. We identified cDNAs encoding the enzyme by using antibodies to screen a bovine intermediate pituitary lambda gt11 expression library. Antibodies to a beta-galactosidase/PAM fusion protein removed PAM activity from bovine pituitary homogenates. The 108,207 dalton protein predicted by the complete cDNA is approximately twice the size of purified PAM. An NH2-terminal signal sequence and short propeptide precede the NH2 terminus of purified PAM. The sequences of several PAM cyanogen bromide peptides were localized in the NH2-terminal half of the predicted protein. The cDNA encodes an additional 430 amino acid intragranular domain followed by a putative membrane spanning domain and a hydrophilic cytoplasmic domain. The forms of PAM purified from bovine neurointermediate pituitary may be generated by endoproteolytic cleavage at a subset of the 10 pairs of basic amino acids in the precursor. High levels of PAM mRNA were found in bovine pituitary and cerebral cortex. In corticotropic tumor cells, levels of PAM mRNA and pro-ACTH/endorphin mRNA were regulated in parallel by glucocorticoids and CRF.