pH-regulated Secretion of a Glyceraldehyde-3-Phosphate Dehydrogenase from Streptococcus gordonii FSS2: Purification, Characterization, and Cloning of the Gene Encoding this Enzyme

• Published in: Journal of dental research Vol. 80; no. 1; pp. 371 - 377
• Main Authors: Nelson, D., Goldstein, J.M., Boatright, K., Harty, D.W.S., Cook, S.L., Hickman, P.J., Potempa, J., Travis, J., Mayo, J.A.
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01.01.2001; SAGE PUBLICATIONS, INC
• Subjects: Adaptation, Physiological; Amino Acid Sequence; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - isolation & purification; Bacterial Proteins - secretion; Cloning, Molecular; Culture Media - chemistry; Dentistry; Gene Dosage; Genes, Bacterial; Glyceraldehyde-3-Phosphate Dehydrogenases - chemistry; Glyceraldehyde-3-Phosphate Dehydrogenases - genetics; Glyceraldehyde-3-Phosphate Dehydrogenases - isolation & purification; Glyceraldehyde-3-Phosphate Dehydrogenases - secretion; Hydrogen-Ion Concentration; Molecular Weight; Protein Binding; Streptococcus pyogenes - enzymology; Streptococcus pyogenes - physiology; Streptococcus sanguis - enzymology; Streptococcus sanguis - physiology; pH; GAPDH; Streptococcus gordonii
• ISSN: 0022-0345; 1544-0591
• DOI: 10.1177/00220345010800011301

Streptococcus gordonii and other viridans streptococci (VS) are primary etiologic agents of infective endocarditis, despite being part of the normal oral microflora. Recently, a surface-bound glyceraldehyde-3 -phosphate dehydrogenase (GAPDH) has been found on the cells of all tested streptococcal species, where it has been implicated as a virulence factor. In contrast, we observed that a soluble extracellular GAPDH was the major secreted protein from S. gordonii FSS2, an endocarditis strain. The biochemical properties and gene sequence of S. gordonii GAPDH are almost identical to those of other streptococcal GAPDHs. Growth at defined pHs showed that secretion of GAPDH is regulated by environmental pH. GAPDH was primarily surface-associated at growth pH 6.5 and shifted to > 90% secreted at growth pH 7.5. Others have identified S. gordonii promoters that are up-regulated by a pH shift similar to that experienced by organisms entering the blood stream (neutral) from the oral cavity (slightly acid). Analysis of our results suggests that secretion of GAPDH may be a similar adaptation by S. gordonii.