A novel antibacterial agent derived from the C-terminal domain of streptococcus mutans GTP-binding protein

A decapeptide, P1, homologous to part of the Streptococcus mutans G-protein (SGP) and the Escherichia coli Era protein, was synthesized and examined for growth-inhibitory effects. When P1 10 mg/L was added to E. coli DH5, the viability of the cells was reduced by 13%. Addition of lauric acid enhanced the bactericidal effects of P1 (68% killing in the presence of P1 plus lauric acid). Similar enhancements were observed for mono lauroyl-rac-glycerol (MLG) and sodium dodecyl sulphate (SDS). In cultures treated with both P1 and MLG, there were more elongated cells than in cultures treated with detergent or peptide alone. As with E. coli, the bactericidal effects of P1 on S. mutans were significantly enhanced in the presence of the detergent lauric acid. The combination of the two effectors produced >90% killing of S. mutans. Likewise, the combined action of P1 plus lauric acid reduced the viability of Listeria monocytogenes. P1 did not appear to be toxic to human gingival epithelial cells when added at concentrations < or = 1000 mg/L. Therefore, P1 has properties which could allow it to be used as an antibacterial agent.