Interaction of salivary alpha-amylase and amylase-binding-protein A (AbpA) of Streptococcus gordonii with glucosyltransferase of S. gordonii and Streptococcus mutans.
BACKGROUND
Glucosyltransferases (Gtfs), enzymes that produce extracellular glucans from dietary sucrose, contribute to dental plaque formation by Streptococcus gordonii and Streptococcus mutans. The alpha-amylase-binding protein A (AbpA) of S. gordonii, an early colonizing bacterium in dental plaque, interacts with salivary amylase and may influence dental plaque formation by this organism. We examined the interaction of amylase and recombinant AbpA (rAbpA), together with Gtfs of S. gordonii and S. mutans.


RESULTS
The addition of salivary alpha-amylase to culture supernatants of S. gordonii precipitated a protein complex containing amylase, AbpA, amylase-binding protein B (AbpB), and the glucosyltransferase produced by S. gordonii (Gtf-G). rAbpA was expressed from an inducible plasmid, purified from Escherichia coli and characterized. Purified rAbpA, along with purified amylase, interacted with and precipitated Gtfs from culture supernatants of both S. gordonii and S. mutans. The presence of amylase and/or rAbpA increased both the sucrase and transferase component activities of S. mutans Gtf-B. Enzyme-linked immunosorbent assay (ELISA) using anti-Gtf-B antibody verified the interaction of rAbpA and amylase with Gtf-B. A S. gordonii abpA-deficient mutant showed greater biofilm growth under static conditions than wild-type in the presence of sucrose. Interestingly, biofilm formation by every strain was inhibited in the presence of saliva.


CONCLUSIONS
The results suggest that an extracellular protein network of AbpA-amylase-Gtf may influence the ecology of oral biofilms, likely during initial phases of colonization.
Chaudhuri
Biswendu
B
Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, New York, USA. bc28@buffalo.edu <bc28@buffalo.edu>
Rojek
Jennifer
J
Vickerman
M Margaret
MM
Tanzer
Jason M
JM
Scannapieco
Frank A
FA
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D004926:Escherichia coli; D017353:Gene Deletion; D005964:Glucosyltransferases / Q000378:metabolism*; D006801:Humans; D010957:Plasmids; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D012463:Saliva / Q000201:enzymology*; D013291:Streptococcus / Q000737:chemistry*; D013295:Streptococcus mutans / Q000737:chemistry; D000516:alpha-Amylases / Q000378:metabolism*
C112818:AbpA protein, Streptococcus gordonii; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D011994:Recombinant Proteins; D005964:Glucosyltransferases; C101905:GtfG protein, Streptococcus gordonii; D000516:alpha-Amylases