A MGL-LIKE OPERON IN TREPONEMA-PALLIDUM, THE SYPHILIS SPIROCHETE

A 38-kDa lipoprotein of Treponema pallidum subsp. pallidum (T. pallidu m), the syphilis spirochete, previously was identified as a putative h omolog of E. coli MglB [Becker et al. (1994) Infect. Immun. 62, 1381-1 391]. In the present study, genome walking in regions adjacent to the T. pallidum 38-kDa lipoprotein gene has identified three contiguous ge nes (tp-mglB [formerly tpp38], tp-mglA, and tp-mglC) which appear to c omprise a mgl-like operon in T. pallidum. A prominent transcript corre sponding to tp-mglB, the first gene of the operon which encodes the ca rbohydrate receptor, is synthesized by T. pallidum along with lesser a bundant transcript(s) corresponding to the entire T. pallidum mgl oper on. An active promoter 135 bp upstream of tp-mglB is believed to direc t mRNA synthesis for the operon. This is the first membrane protein-en coding operon of T. pallidum for which a putative function (glucose im port) has been assigned. Furthermore, by analogy with E. coli MglB whi ch interacts with the sensory transducer Trg to induce a chemotactic r esponse, it is possible that T. pallidum also contains a homolog of E. coli Trg or other methyl-accepting chemotaxis proteins. The existence of a mgl operon in T. pallidum thus may have important implications w ith respect to T. pallidum survival, tissue dissemination, and sensory transduction during virulence expression.