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PubMed1983

Immunochemical properties of glucosyltransferases from Streptococcus mutans.

Antiserum against purified mutansynthetase (EC 2.4.1.?) of Streptococcus mutans 6715 (serotype g), which is responsible for the synthesis of water-insoluble glucan (ISG) in the presence of both sucrose and water-soluble glucan, was prepared. The specificity of the antiserum was tested by using crude enzyme preparations (CEPs) of S. mutans strains of various serotypes. On immunodiffusion, the antiserum cross-reacted with CEPs from strains of serotypes a (HS-6 and AHT), d (OMZ176), and g (OMZ65 and KIR), but not with those from strains of serotypes b (BHT and FA-1) and c (GS-5 and Ingbritt). The antiserum inhibited the synthesis of ISG by crude or purified mutansynthetase of S. mutans 6715. The activities of ISG synthesis by CEPs from the strains antigenically related in the foregoing immunodiffusion were inhibited by the antiserum against strain 6715 mutansynthetase. The antiserum, however, also inhibited the enzyme activity of the strains of serotype b. The finding that the antiserum against purified dextransucrase of S. mutans HS-6 inhibited ISG synthesis by a CEP of strain HS-6 and also by CEPs of antigenically related strains suggested that dextransucrase activity is involved in ISG synthesis.

Cross Reactions↗

PubMed1996

Immunologic characteristics of a Streptococcus mutans glucosyltransferase B sucrose-binding site peptide-cholera toxin B-subunit chimeric protein.

Glucosyltranferases (Gtfs) produced by the mutans streptococci are recognized as virulence factors in dental caries, and the inhibition of Gtfs by secretory immunoglobulin A is predicted to provide protection against this disease. The basis of such mucosal immunity is linked to the ability to reliably stimulate production of secretory immunoglobulin A against Gtfs. In this regard, we are exploring the immunogenicities of various Gtf peptides genetically fused to the B subunit of cholera toxin (CTB), a known mucosal adjuvant. In this work, we have created a gene fusion linking the GtfB active-site (AS) peptide DANFDSIRVDAVDNVDADLLQIA to the amino terminus of CTB. This sequence, deduced from the nucleotide sequence of gtfB from Streptococcus mutans GS5, has been found to be strongly conserved in Gtfs from several mutans streptococci. We have purified this recombinant protein (AS:CTB) from Escherichia coli carrying the fusion gene under the control of the lactose operon promoter. This protein was immunogenic in rabbits and produced specific serum antibodies against both the Gtf peptide and the CTB moiety. The antiserum was tested for its ability to inhibit GtfB activity obtained from a mutant of S. mutans able to make only this enzyme and none of the other usual Gtfs or fructosyltransferase. Approximately 50% of the GtfB activity was inhibited in such assays. These results suggest that the AS of this enzyme is accessible to antibody binding and that this region of the protein may be considered a vulnerable target for vaccine design and development. The AS:CTB was able to bind GM1, ganglioside in enzyme-linked immunosorbent assays, indicating that the recombinant protein retained this property, which is though to be critical to the mucosal immunoadjuvant properties of CTB. Thus, this protein may be promising as a candidate anticaries vaccinogen alone or in combination with other Gtf peptides or conjugates.

Adjuvants, Immunologic↗

PubMed1999

Isolation of an active catalytic core of Streptococcus downei MFe28 GTF-I glucosyltransferase.

Truncated variants of GTF-I from Streptococcus downei MFe28 were purified by means of a histidine tag. Sequential deletions showed that the C-terminal domain was not directly involved in the catalytic process but was required for primer activation. A fully active catalytic core of only 100 kDa was isolated.

Bacterial Proteins↗

PubMed2005

Functional and topological analysis of the Burkholderia cenocepacia priming glucosyltransferase BceB, involved in the biosynthesis of the cepacian exopolysaccharide.

The BceB protein of the cystic fibrosis mucoid isolate Burkholderia cenocepacia IST432 is proposed to catalyze the first step of the exopolysaccharide repeat unit assembly. Extracts of Escherichia coli cells overexpressing BceB were shown to contain glycosyltransferase activity and mediate incorporation of glucose-1-phosphate into membrane lipids. The amino acid sequence of BceB exhibits two conserved regions, one comprising two invariant aspartic acid residues (Asp339 and Asp355) that are essential for catalysis, as substantiated by site-directed mutagenesis, and the other comprising a putative Rossmann fold motif. The results of protein topology analysis using PhoA and LacZ fusions supported in silico predictions that BceB has at least six transmembrane segments and two major cytoplasmic loops comprising the conserved regions described above.

Amino Acid Sequence↗

PubMed1985

Temperature-sensitive mutants in rfaI and rfaJ, genes for galactosyltransferase I and glucosyltransferase II, for synthesis of lipopolysaccharide in Salmonella typhimurium.

Certain rough mutants of Salmonella typhimurium LT2 were shown to be temperature sensitive for the production of lipopolysaccharide (LPS). When grown at the restrictive temperature (42 or 45 degrees C), the cells contained LPS deficient in O (somatic) side chains, based on phage-sensitivity data and gel electrophoresis of the LPS. Cells grown at the permissive temperature, 30 degrees C, made LPS resembling that of smooth cells. The mobility of the LPS in gels, the phage sensitivity patterns, and gas chromatographic analysis indicate that LPS of 45 degrees C-grown cells of SA126 (rfaJ3012) is of chemotype Rb2, with one glucose and two galactose units (and thus inferred to be due to a mutation in rfaJ), and LPS of 45 degrees C-grown cells of SA134 (rfa13020) is of chemotype Rb3, with one glucose and one galactose unit (inferred to be rfaI). These inferences were confirmed, for pKZ26 (pBR322-rfaGBIJ) and pKZ27 (pBR322-rfaGBI) both complement rfaI3020, but only pKZ26 complemented rfaJ3012. In addition, pKZ26 carrying a Tn5 insertion resulting in loss of complementation of a known rfaJ mutation, but not of rfaG, B, or I, also resulted in loss of rfaJ3012 complementation. Based on gel analysis, there is a small amount of the LPS containing smooth side chains in cells of SA126 grown at 45 degrees C; following a switch to 30 degrees C, the amount of LPS with O side chains gradually increased, and the amount of core LPS was reduced, though even after 3 h the LPS does not fully resemble that of smooth strains.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA Restriction Enzymes↗

PubMed1998