Characterization of a novel potential peptide import system of Treponema denticola. Characterization of a novel potential peptide import system of Treponema denticola

Treponema denticola is a major etiologic agent of chronic periodontitis. On the outer sheath of T. denticola, several proteins such as the major outer sheath protein were detected, and among them, a 95 kDa protein has not yet been characterized. The aim of this study was to characterize the function of this 95 kDa protein. A gene encoding this 95 kDa protein (TDE_1072) of T. denticola was inactivated by homologous recombination. We compared growth curves between the TDE_1072 mutant and wild-type strains as well as differences in gene expression by DNA microarray analysis. Differentially expressed genes identified by microarray analysis were confirmed by quantitative reverse transcription-polymerase chain reaction. The proteins encoded by TDE_1072, TDE_1073, TDE_1074, TDE_1075, and TDE_1076 shared respective similarities to the substrate-binding domain (DppA) of an ABC-type dipeptide/oligopeptide/nickel transport system, and to the permease component (DppB and DppC) and ATPase component (DppD and DppF) of an ABC-type dipeptide/oligopeptide/nickel transport system. Inactivation of dppA attenuated the growth of T. denticola and down-regulated expression of dppB-dppF. In contrast, expression of oppB-oppF was upregulated in the mutant. Our findings indicate that TDE_1072 may be a potential periplasmic solute binding protein encoded by dppA that is involved in the organization of a peptide uptake system with dppB-dppF. Overall design: Comparison of 2 strains of T. denticola. Treponema denticola ATCC 35405 and I-1 was cultured in TYGVS medium for 24-48 h. Profile of gene expression of T. denticola I-1 was compared to that of ATCC 35405.