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PubMed2004

Peptide mapping of a novel discontinuous epitope of the major surface adhesin from Streptococcus mutans.

Guy's 13 is a mouse monoclonal antibody that specifically recognizes the major cell-surface adhesion protein SA I/II of Streptococcus mutans, one of the major causative agents of dental caries. Passive immunization with Guy's 13 prevents bacterial colonization in humans. To help elucidate the mechanism of prevention of colonization conferred by this antibody, the SA I/II epitope recognized by Guy's 13 was investigated. It was previously established that the epitope is conformational, being assembled from two non-contiguous regions of SA I/II. In the current study, using recombinant fragments of SA I/II and, ultimately, synthetic peptides, the discontinuous epitope was localized to residues 170-218 and 956-969. This work describes the mapping of a novel discontinuous epitope that requires an interaction between each determinant in order for epitope assembly and recognition by antibody to take place. Guy's 13 binds to the assembled epitope but not to these individual epitope fragments. The assembled epitope results from the interaction between the individual antigenic determinants and can be formed by mixing together determinants present on separate polypeptide chains. The data are consistent with one of the epitope fragments adopting a polyproline II-like helical conformation.

Adhesins, Bacterial↗
PubMed1984

Characterization of the Escherichia coli SSB-113 mutant single-stranded DNA-binding protein. Cloning of the gene, DNA and protein sequence analysis, high pressure liquid chromatography peptide mapping, and DNA-binding studies.

The ssb-113 (formerly lexC113) gene encoding a mutant single-stranded DNA binding protein (SSB) has been cloned into plasmid pSC101 resulting in 5- to 10-fold more mutant protein than strains carrying only one (chromosomal) copy of the gene. Analysis of tryptic and chymotryptic peptides of the mutant protein by high pressure liquid chromatography and solid phase protein sequencing has shown that the ssb-113 mutation results in the substitution of serine for proline at residue 176 of SSB. This change could only occur in one step by a C leads to T transition in the DNA sequence. Physicochemical studies of the homogeneous mutant protein have shown that it binds as well as wild type SSB to single-stranded DNA and that it is a slightly better helix-destabilizing protein than wild type SSB as measured by its ability to lower the thermal melting transition of poly[d(A-T)]. In vivo studies of ssb-113 strains carrying the cloned ssb-113 gene in pSC101 have shown that overproduction of the mutant protein does not complement the temperature-sensitive conditional lethality caused by the ssb-113 mutation when present in single gene copy in contrast to effects recently observed in ssb-1 strains overproducing the ssb-1 encoded protein (Chase, J. W., Murphy, J. B., Whittier, R. F., Lorensen, E., and Sninsky, J. J. (1983) J. Mol. Biol. 164, 193-211). Also noted in this report are two corrections to the DNA sequence of wild type SSB, one of which places glycine (codon GGC) at residue 133 rather than serine as previously reported (Sancar, A., Williams, K. R., Chase, J. W., and Rupp, W. D. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 4274-4278). The second correction to the DNA sequence is in the serine 39 codon, previously reported to be TCA and now correctly shown to be TCC.

Amino Acid Sequence↗
PubMed1980

Comparative tryptic peptide mapping studies suggest a role in cell transformation for the gag-related protein of avian erythroblastosis virus and avian myelocytomatosis virus strains CMII and MC29.

The gag-related proteins found in cells transformed by avian erythroblastosis virus (AEV) and the avian myelocytomatosis viruses MC29 and CMII have been compared by tryptic peptide fingerprinting. A comparison of the methionine-containing tryptic peptides of the AEV 75-kilodalton protein, the CMII 90-kilodalton protein, and the MC29 110-kilodalton protein with the gag gene product Pr76 of their naturally occurring helper leukemia viruses enabled us to distinguish those peptides related to the gag gene from the non-gag-related peptides. The 12 non-gag peptides found in the AEV 75-kilodalton protein were unique to this protein and not found in the MC29 110-kilodalton or CMII 90-kilodalton proteins. In contrast, the MC29 110-kilodalton protein shared two methionine-containing non-gag tryptic peptides with the CMII 90-kilodalton protein. When these experiments were repeated with [14C]lysine and [14C]arginine as the labeled amino acids, the MC29 110-kilodalton protein and the CMII 90-kilodalton protein were found to share 30 out of approximately 40 non-gag-related peptides. These results demonstrate that viruses with a similar transformation spectrum synthesize related proteins and suggest that the gag-related proteins represent the transforming proteins of the replication-defective avian leukemia viruses.

Alpharetrovirus↗
PubMed1982

Peptide mapping studies of the chromogranins and of two chromaffin granule proteoglycans.

The chromogranins, a family of related acidic glycoproteins, and two chondroitin sulfate/dermatan sulfate proteoglycans were isolated from the soluble contents of bovine adrenal chromaffin granules by chromatography on DEAE-cellulose. These chromaffin granule matrix glycoconjugates were treated with trypsin, and the resulting peptides were fractionated by HPLC. The two proteoglycans, which differ in their concentration of glycosaminoglycans and glycoprotein oligosaccharides, yielded almost identical peptide patterns and would both appear to have the same protein moiety. The peptide profile of the proteoglycans differs, however, from that of the chromogranins, which they closely resemble in terms of amino acid composition. The various chromogranin fractions obtained by gel filtration were also found to have significant differences in the chromatographic patterns of their tryptic peptides.

Adrenal Medulla↗