Amino acid sequence of the N-terminal domain of yam (Dioscorea japonica) aerial tuber acidic chitinase. Evidence for the presence of a wheat germ agglutinin domain in matured acidic chitinase from unstressed tuber

The amino acid sequence of the N-terminal domain of acidic chitinase from unstressed aerial tuber was determined and proved the presence of an N-terminal domain in acidic chitinase. The amino acid sequence was determined on a pyroglutamylaminopeptidase-treated N-terminal fragment of V8 protease and on chymotryptic peptides of this fragment. The sequence determined revealed 8 residues deletion and 2 residues insertion as compared with the N-terminal domain of tobacco basic chitinase. The N-terminal domain determined showed a homology of 40% and 52% with the N-terminal domain of tobacco basic chitinase and wheat germ agglutinin, respectively.Abbreviations DABITC,4-N,N dimethylaminoazobenzene 4-isothiocyanate - PITC phenylisothiocyanate - Cm carboxymethyl - WGA wheat germ agglutinin - TFA trifluoroacetic acid - PGAP pyroglutamylaminopeptidase     

A comparsion of glycopeptides from the transferrins of several species.

1. The carbohydrate compositions of human, pig and cattle transferrins and duck ovotransferrin have been determined. 2. Glycopeptides have been prepared from these transferrins and their carbohydrate compositions and amino acid sequences determined. One of the glycopeptides from human transferrin carries the C-terminal residue of the protein. 3. Each tranferrrin yielded two glycopeptides that appeared to be identical in carbohydrate composition but different in amino acid sequence. The two glycopeptides have been distinguished as type A, in which the residue following Asn(CHO)(where CHO represents a carbohydrate moiety) is a basic amino acid and type B in which Asn(CHO) is followed by a neutral aliphatic amino acid. Cattle transferrin is exceptional in having two glycopeptides in which this position is occupied by serine. 4. It is suggested that each molecule of human and cattle transferrin and duck ovotransferrin carries an average of two carbohydrate prosthetic groups. Hen and pig transferrins appear to carry only one carbohydrate group per mol of protein. 5. The N-terminal sequences of hen and duck ovotransferrins and of cattle, human and pig transferrins were also determined.     

Comparison of bovine serum transferrin A and D2. II. Glycopeptides

Glycopeptides are isolated from subtilisin and pronase digests of whole bovine serum transferrin A and D2. The two variants yield glycopeptides with identical amino acid composition. Hence, there is probably no amino acid substitution in this region of the peptide chain. Amino acid sequence determination of one glycopeptide (subtilisin glycopeptide 8) gives the sequence: (CHO)Asn-Ser-Ser-Leu-Cys. This sequence is identical with that of residues 491-495 of the sequence for human serum transferrin (MacGillivray et al., 1982) except that in the bovine transferrin, Asp is replaced by Asn, enabling carbohydrate attachment. A second glycopeptide sequence Arg-(CHO)Asn-Ala-Thr-Tyr is observed, and the significance discussed in relation to carbohydrate moieties of serum glycoproteins.     

The structure of a naturally occurring 10K polypeptide derived from the amino terminus of bovine thyroglobulin

A combination of data derived from peptide sequencing and nucleic acid sequencing of cloned cDNA fragments has been used to define the complete amino acid sequence of a 10,000 M.W., thyroxine containing polypeptide derived from bovine thyroglobulin. This fragment, TG-F, which was obtained following reduction and alkylation, has been placed at the amino terminus of the parent protein with hormone located at residue 5 in the primary sequence of the thyroglobulin molecule. The carboxyl terminal sequence of this fragment -Cys-Gln-Leu-Gln is found on the N-terminal side of a lys residue, suggesting that the peptide bond cleavage which occurs to produce this 80 residue fragment from the parent (330K) thyroglobulin chain is a gln-lys. In addition, the amino acid sequence of this 10K fragment contains: No sequence which would be a substrate for glycosylation and no carbohydrate. Several repeated homologous amino acid sequences. A striking number of beta-bends predicted from Chou-Fasman analyses, particularly near its carboxyl terminus.     

Isolation, molecular and functional properties of the C-terminal domain of colicin A

Partial proteolytic digestion of colicin A with bromelain allowed the isolation of a 20-kd fragment. This fragment has been purified to homogeneity and its molecular properties have been studied. The sequence of the 54 N-terminal amino acid residues has been determined by automated Edman degradation. This sequence is identical to that of the predicted amino acid sequence of the 20-kd C-terminal part of the colicin A polypeptide deduced from the nucleotide sequence of the caa gene. This polypeptide can produce channels in phospholipid planar bilayers of the same size as those formed by colicin A. However, the voltage-dependence for opening and closing was drastically altered in the peptide fragment channels. The latter, in contrast to colicin A channels, remained open over a wide range of voltage. Large negative potentials were required to close the peptide fragment channels although opening took place in the same voltage range as for colicin A ionic pores.     

The localization of a vitamin K-induced modification in an N-terminal fragment of human prothrombin

1. The N-terminal fragment (PF-I) split off from prothrombin during coagulation was purified to homogeneity from human serum. 2. The apparent molecular weight is 27000+/-2000 in sodium dodecyl sulphate-polyacrylamide-gel electrophoresis, whereas a value of about 19600 is obtained by calculation based on amino acid and carbohydrate analyses. The N-terminal sequence is an Ala-Asx bond. The fragment contains about 16% carbohydrate, binds phospholipids in the presence of Ca(2+) and is adsorbed to BaSO(4). The pK(a) of its BaSO(4)-binding group(s) is 3.1-3.5. 3. By CNBr cleavage of fragment PF-I two peptides (C-1 and C-2) were obtained with molecular weights of about 5900 (C-2) and 12400 (C-1) on the basis of amino acid and carbohydrate analyses. Only the smaller (N-terminal) peptide is adsorbed to BaSO(4) and, since the ability of the whole protein to bind to BaSO(4) is known to be absent in samples obtained from patients treated with vitamin K antagonists, this peptide probably contains the site of a modification to the structure of the protein which occurs during biosynthesis and depends on vitamin K. This peptide does not contain hexosamine or sialic acid.     

Comparison of the amino acid sequences of hen plasma-, yolk-, and white-riboflavin binding proteins

The amino acid sequence of hen egg yolk-riboflavin binding protein (yolk-RBP) was determined by conventional methods. The sequence was identical with that of hen egg white-riboflavin binding protein except that their carboxyltermini were different, that of yolk-RBP lacked 11 or 13 amino acid residues, while hen plasma-RBP had the same C-terminal sequence as white-RBP. This indicated that the C-terminal 11 or 13 amino acid residues in plasma-RBP might be cleaved off during the incorporation from the blood into the oocyte or in the yolk fluid. Yolk-RBP had the same characteristics as white-RBP, such as N-terminal pyroglutamic acid, polymorphism in the amino acid sequence (Lys/Asn) at the fourteenth residue from the N-terminal end, carbohydrate chains attached to both Asn(36) and Asn(147) residues, and phosphate groups bound to some serine residues in the sequence of Ser(185) to Ser(197) as a cluster. These results led us to the conclusion that yolk- and white-RBPs are bio-synthesized from the same gene in the different organs (liver and oviduct). The carbohydrate composition of yolk-RBP was identical to that of plasma-RBP but different from that of white-RBP showing that the processing of the carbohydrate chains in the liver was different from that in the oviduct.     

Purification and characterization of a Neu5Acalpha2-6Galbeta1-4Glc/GlcNAc-specific lectin from the fruiting body of the polypore mushroom Polyporus squamosus

A lectin has been purified from the carpophores of the mushroom Polyporus squamosus by a combination of affinity chromatography on beta-D-galactosyl-Synsorb and ion-exchange chromatography on DEAE-Sephacel. Gel filtration chromatography, SDS-polyacrylamide gel electrophoresis, and N-terminal amino acid sequencing indicated that the native lectin, designated P. squamosus agglutinin, is composed of two identical 28-kDa subunits associated by noncovalent bonds. P. squamosus agglutinin agglutinated human A, B, and O and rabbit red blood cells but precipitated only with human alpha(2)-macroglobulin, of many glycoproteins and polysaccharides tested. The detailed carbohydrate binding properties of the purified lectin were elucidated using three different approaches, i.e. precipitation inhibition assay (in solution binding assay), fluorescence quenching studies, and glycolipid binding by lectin staining on high-performance thin layer chromatography (solid-phase binding assay). Based on the results obtained by these assays, we conclude that although the P. squamosus lectin binds beta-D-galactosides, it has an extended carbohydrate-combining site that exhibits highest specificity and affinity toward nonreducing terminal Neu5Acalpha2, 6Galbeta1,4Glc/GlcNAc (6'-sialylated type II chain) of N-glycans (2000-fold stronger than toward galactose). The strict specificity of the lectin for alpha2,6-linked sialic acid renders this lectin a valuable tool for glycobiological studies in biomedical and cancer research.     

Characterization and comparison of arcelin seed protein variants from common bean

Four variants of arcelin, an insecticidal seed storage protein of bean, Phaseolus vulgaris L., were investigated. Each variant (arcelin-1, -2, -3, and -4) was purified, and solubilities and M_rs were determined. For arcelins-1, -2, and -4, the isoelectric points, hemagglutinating activities, immunological cross-reactivities, and N-terminal amino acid sequences were determined. On the basis of native and denatured M_rs, the variants were classified as being composed of dimer protein (arcelin-2), tetramer protein (arcelins-3 and -4), or both dimer and tetramer proteins (arcelin-1). Although the dimer proteins (arcelins-1d and -2) could be distinguished by M_rs and isoelectric points, they were identical for their first 37 N-terminal amino acids and had similar immunological cross-reactions, and bean lines containing these variants had a DNA restriction fragment in common. The tetramer proteins arcelin-1t and arcelin-4 also could be distinguished from each other based on M_rs and isoelectric points; however, they had similar immunological cross-reactions and they were 77 to 93% identical for N-terminal amino acid composition. The similarities among arcelin variants, phytohemagglutinin, and a bean α-amylase inhibitor suggest that they are all encoded by related members of a lectin gene family.     

Characterization of Nontoxic-Nonhemagglutinin Component of the Two Types of Progenitor Toxin (M and L) Produced by Clostridium botulinum Type D CB-16

A 9.8-kbp DNA fragment which contained a neurotoxin gene and its upstream region was cloned from Clostridium botulinum type D strain CB-16. Nucleotide sequencing of the fragment revealed that genes encoding for hemagglutinin (HA) subcomponents and one for a nontoxic-nonhemagglutinin (NTNH) component were located upstream of the neurotoxin gene. This strain produced two toxins of different molecular size (approximately 300 kDa and 500 kDa) which were designated as progenitor toxins (M and L toxins). The molecular size of the NTNH component of L toxin was approximately 130 kDa on SDS-PAGE and its N-terminal amino acid sequence was M-D-I-N-D-D-L-N-I-N-S-P-V-D-N-K-N-V-V-I which agreed with that deduced from the nucleotide sequence. In contrast, the M toxin had a 115-kDa NTNH component whose N-terminal sequence was S-T-I-P-F-P-F-G-G-Y-R-E-T-N-Y-I-E, corresponding to the sequence from Ser141 of the deduced sequence. A 15-kDa fragment, which was found to be associated with an M toxin preparation, possessed the same N-terminal amino acid sequence as that of the 130-kDa NTNH component. Furthermore, five major fragments generated by limited proteolysis with V8 protease were shown to have N-terminal amino acid sequences identical to those deduced from the nucleotide sequence of 130-kDa NTNH. These results indicate that the 130-kDa NTNH of the L toxin is cleaved at a unique site, between Thr and Ser, leading to the 115-kDa NTNH of the M toxin.     

Trypanosoma congolense: Surface glycoproteins of two early bloodstream variants: II. Purification and partial chemical characterization

Two sequential variant-specific glycoproteins have been purified from two variants of Trypanosoma congolense expressed during a relapsing infection. Isolation of the two glycoproteins, termed VSG-1 and VSG-2, respectively, employed glycerol lysis followed by purification on concanavalin A, Sephadex G-25, and gradient-eluted DE-52 columns. Partially purified VSG proteins were immunologically cross-reactive, but highly purified VSGs showed no cross-reactivity under the conditions employed. Both VSG-1 and VSG-2 consisted of a triplet of polypeptides. Although each member of a triplet subset could be distinguished by isoelectric focusing, all three gave identical N-terminal amino acid sequences and nearly identical tryptic peptide maps. The members of the VSG-1 polypeptide subset differed from those of the VSG-2 subset both with regard to N-terminal amino acid sequence and in tryptic peptide map patterns. Comparison of N-terminal sequences of VSG-1 and VSG-2 did, however, show that the sequences could be aligned to give a modest degree of amino acid homology (27%). This alignment also produced a minimum in the number of two-base changes, suggesting that the observed homology is not a coincidence and that these two proteins may well have arisen by gene duplication followed by retention of multiple point mutations.     

Amino acid sequence studies on cyanogen bromide peptides of chicken caldesmon which bind to calmodulin

Three major calmodulin-binding cyanogen bromide peptides (fragments A, B, and D) were isolated from chicken gizzard muscle caldesmon and their amino acid sequences were determined. The molecular masses of fragments A, B, and D were estimated to 16, 12, and 9 kDa, respectively, by SDS-urea polyacrylamide gel electrophoresis. Fragment A was composed of 102 amino acid residues and contained homoserine at the C terminus. The amino acid sequence from the 37th residue of fragment A corresponds to the N-terminal sequence of the 15 kDa peptide which was obtained by thrombin digestion [Mornet, D., Audemard, E., & Derancourt, J. (1988) Biochem. Biophys. Res. Commun. 154, 564-571]. Thrombin 15 kDa peptide binds to F-actin but does not bind to calmodulin. Thus the N-terminal 36 residues and the C-terminal part from the 37th residue of fragment A are supposed to bind to calmodulin and F-actin, respectively. The sequences of fragments B and D were identical, but fragment D was composed of 64 amino acid residues and ended with tryptophan, whereas fragment B was of 98 or 99 amino acid residues and ended with proline. Both fragments B and D are supposed to be the C-terminal peptides of chicken caldesmon. Fragment B had heterogeneous sequences at the C-terminal region. These results can explain the reported heterogeneity of chicken caldesmon in charge and molecular mass.     

Purification of a soluble and a wall-bound form of beta-glucosidase from Mucor racemosus.

beta-Glucosidase activity in crude extracts of Mucor racemosus exists in a soluble form and in a wall-bound form which sediments at 3,500 x g. The soluble form and a wall-bound form were purified to homogeneity by ammonium sulfate fractionation. DEAE-Sephadex chromatography, and SP-Sephadex chromatography. Both forms were identical in all parameters measured. Each enzyme is a glycoprotein of 91,000 daltons, with an identical amino acid composition and N-terminal amino acid of lysine; both contain about 10% carbohydrate. Both forms catalyze the hydrolysis of cellobiose and p-nitrophenyl-beta-D-glucoside with identical kinetic constants.     

Human complement component C4. Structural studies on the fragments derived from C4b by cleavage with C3b inactivator.

1. One of the activation products of C4, C4b, was prepared, and the reactive thiol group on the alpha'-chain was radioactively labelled with iodo[2-14C]acetic acid. The alpha'-chain was isolated and the N-terminal amino acid sequence of the first 13 residues was determined. 2. C4b was cleaved by C3bINA in the presence of C4b-binding protein and C4d and C4c isolated. The radioactive label and therefore the reactive thiol group were located to C4d. 3. C4c was reduced and alkylated and the two alpha'-chain fragments of C4c were separated. 3. The molecular weights, amino acid analyses and carbohydrate content of the three alpha'-chain fragments were determined. C4d has a mol.wt. of 44500 and a carbohydrate content of 6%. The two alpha'-chain fragments of C4c have mol.wts. of 25000 (alpha 3) and 12000 (alpha 4) and carbohydrate contents of 10 and 22% respectively. 4. The N-terminal amino acid sequences of C4d, the alpha 3 and the alpha 4 fragments were determined for 18, 24 and 11 residues respectively and, by comparison with the N-terminal sequence of the C4b alpha'-chain, the 25000-mol.wt. fragment (alpha 3) was shown to be derived from the N-terminal part of the alpha'-chain. 5. C-Terminal analyses were done on the alpha'-chain and its three fragments. Arginine was found to be the C-terminal residue of C4d and of the alpha 3 fragment. The C-terminal residue of the alpha'-chain and of the alpha 4 fragment could not be identified. The order of the three fragments of the alpha'-chain is therefore: alpha 3(25000)--C4d(44500)--alpha 4(12000). The specificity of C3bINA is for an Arg--Xaa peptide bond.     

Studies on chemical modification of cold agglutinin from the snail Achatina fulica.

The cold agglutinin isolated from the albumin gland of the snail Achatina fulica was modified with various chemical reagents in order to detect the amino acids and/or carbohydrate residues present in its carbohydrate-binding sites. Treatment with reagents considered specific for modification of lysine, arginine and tryptophan residues of the cold agglutinin did not affect the carbohydrate-binding activity of the agglutinin. Modification of tyrosine residues showed some change. However, modification with carbodiimide followed by alpha-aminobutyric acid methyl ester causes almost complete loss of its binding activity, indicating the involvement of aspartic acid and glutamic acid in its carbohydrate-binding activity. The carbohydrate residues of the cold agglutinin were removed by beta-elimination reaction, indicating that the sugars are O-glycosidically linked to protein part of the molecule. Removal of galactose residues from the cold agglutinin by the action of beta-galactosidase indicated that the galactose molecules are beta-linked. These carbohydrate-modified glycoproteins showed a marked change in agglutination property, i.e. they agglutinated rabbit erythrocytes at both 10 degrees C and 25 degrees C, indicating that the galactose residues of the glycoprotein play an important role in the cold-agglutination property of the glycoprotein. The c.d. data showed the presence of an almost identical type of random-coil conformation in the native cold agglutinin at 10 degrees C and in the carbohydrate-modified glycoprotein at 10 degrees C and 25 degrees C. This particular random-coil conformation is essential for carbohydrate-binding property of the agglutinin.     

Purification, biochemical characterization and N-terminal sequence of a serine-protease with chymotrypsic and collagenolytic activities in a tropical shrimp, Penaeus vannamei (Crustacea, Decapoda).

1. Two chymotrypsin variants, with collagenolytic activities, were purified from the hepatopancreas of Penaeus vannamei using radioactive protein as the substrate. 2. These proteases are very close as far as amino acid composition, molecular weight, inhibitors studies and specificity against small synthetic substrates are concerned. 3. N-terminal amino acid sequences of both variants are identical and are very close to other known crustacean serine proteases.     

DNA-binding activity of amino-terminal domains of the Bacillus subtilis AbrB protein

Two truncated variants of AbrB, comprising either its first 53 (AbrBN53) or first 55 (AbrBN55) amino acid residues, were constructed and purified. Noncovalently linked homodimers of the truncated variants exhibited very weak DNA-binding activity. Cross-linking AbrBN55 dimers into tetramers and higher-order multimers (via disulfide bonding between penultimate cysteine residues) resulted in proteins having DNA-binding affinity comparable to and DNA-binding specificity identical to those of intact, wild-type AbrB. These results indicate that the DNA recognition and specificity determinants of AbrB binding lie solely within its N-terminal amino acid sequence.     

Comparison of bovine serum transferrin A and D2. II. Glycopeptides

Glycopeptides are isolated from subtilisin and pronase digests of whole bovine serum transferrin A and D₂. The two variants yield glycopeptides with identical ami-no acid composition. Hence, there is probably no amino acid substitution in this region of the peptide chain. Amino acid sequence determination of one glycopeptide (subtilisin glycopeptide 8) gives the sequence: (CHO)Asn-Ser-Ser-Leu-Cys. This sequence is identical with that of residues 491–495 of the sequence for human serum transferrin (MacGillivray et al., 1982) except that in the bovine transferrin, Asp is replaced by Asn, enabling carbohydrate attachment. A second glycopeptide sequence Arg-(CHO)Asn-Ala-Thr-Tyr is observed, and the significance discussed in relation to carbohydrate moieties of serum glycoproteins.     

Biologically active domain in somatomedin-binding protein

We have found that human decidua synthesizes a 34K somatomedin-binding protein PP12. Purification of PP12 by immunochemical techniques from human placenta and adjacent membranes has also yielded lower-molecular weight immunoreactive polypeptides designated as PP12B. An individual 21K fragment of somatomedin-binding protein, and a mixture of fragments with molecular weight from 17K to 20K were isolated from this material using high performance liquid chromatography (HPLC). These fragments reacted with antibodies to native PP12 as shown by Western blotting. They all shared the same N-terminal amino acid sequence: Ala-Pro-Trp-Gln-, which is identical with that obtained for PP12. The 21K fragment was shown to bind somatomedin-C, or IGF-I (insulin-like growth factor-I). Since the N-terminal end of the 21K fragment is identical with that of the 34K somatomedin-binding protein, our results suggest that the 21K fragment is the N-terminal part of somatomedin-binding protein, and the somatomedin-binding domain resides in this N-terminal portion.     

The amino acid sequence of peanut agglutinin

The amino acid sequence of peanut (Arachis hypogaea) agglutinin was determined from three major fragments obtained by mild acid cleavage at Asp-Pro peptide bonds. The sequence of 236 amino acids has residues identical to those that form the metal-binding site and the hydrophobic pocket in concanavalin A and other lectins, although the overall similarity is only 42%. In the segments of peanut agglutinin that correspond to the four loops that form the carbohydrate-binding site in concanavalin A and favin, several central residues are homologous, while others show changes to smaller side chains, such as Tyr----Gly. The carbohydrate-binding site of peanut agglutinin may therefore have a similar peptide-backbone architecture, but form a considerably more open cleft.