Amylase-binding protein B of Streptococcus gordonii is an extracellular dipeptidyl-peptidase.
The oral commensal bacterium Streptococcus gordonii interacts with salivary amylase via two amylase-binding proteins, AbpA and AbpB. Based on sequence analysis, the 20-kDa AbpA protein is unique to S. gordonii, whereas the 82-kDa AbpB protein appears to share sequence homology with other bacterial dipeptidases. The aim of this study was to verify the peptidase activity of AbpB and further explore its potential functions. The abpB gene was cloned, and histidine-tagged AbpB (His-AbpB) was expressed in Escherichia coli and purified. Its amylase-binding activity was verified in an amylase ligand binding assay, and its cross-reactivity was verified with an anti-AbpB antibody. Both recombinant His-AbpB and partially purified native AbpB displayed dipeptidase activity and degraded human type VI collagen and fibrinogen, but not salivary amylase. Salivary amylase precipitates not only AbpA and AbpB but also glucosyltransferase G (Gtf-G) from S. gordonii supernatants. Since Streptococcus mutans also releases Gtf enzymes that could also be involved in multispecies plaque interactions, the effect of S. gordonii AbpB on S. mutans Gtf-B activity was also tested. Salivary amylase and/or His-AbpB caused a 1.4- to 2-fold increase of S. mutans Gtf-B sucrase activity and a 3- to 6-fold increase in transferase activity. An enzyme-linked immunosorbent assay verified the interaction of His-AbpB and amylase with Gtf-B. In summary, AbpB demonstrates proteolytic activity and interacts with and modulates Gtf activity. These activities may help explain the crucial role AbpB appears to play in S. gordonii oral colonization.
Chaudhuri
Biswendu
B
Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, Buffalo, New York 14214, USA.
Paju
Susanna
S
Haase
Elaine M
EM
Vickerman
M Margaret
MM
Tanzer
Jason M
JM
Scannapieco
Frank A
FA
D000681:Amylases / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D024142:Collagen Type VI / Q000378:metabolism; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005340:Fibrinogen / Q000378:metabolism; D015870:Gene Expression; D005964:Glucosyltransferases / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D054773:Streptococcus gordonii / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity
C112818:AbpA protein, Streptococcus gordonii; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D024142:Collagen Type VI; D011994:Recombinant Proteins; D005340:Fibrinogen; D005964:Glucosyltransferases; D000681:Amylases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases