Porcella S F, Popova T G, Hagman K E, Penn C W, Radolf J D, Norgard M V
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas 75235, USA.
Gene. 1996 Oct 24;177(1-2):115-21. doi: 10.1016/0378-1119(96)00286-7.
A 38-kDa lipoprotein of Treponema pallidum subsp. pallidum (T. pallidum), the syphilis spirochete, previously was identified as a putative homolog of E. coli MglB [Becker et al. (1994) Infect. Immun. 62, 1381-1391]. In the present study, genome walking in regions adjacent to the T. pallidum 38-kDa lipoprotein gene has identified three contiguous genes (tp-mglB [formerly tpp38], tp-mglA, and tp-mglC) which appear to comprise a mgl-like operon in T. pallidum. A prominent transcript corresponding to tp-mglB, the first gene of the operon which encodes the carbohydrate receptor, is synthesized by T. pallidum along with lesser abundant transcript(s) corresponding to the entire T. pallidum mgl operon. An active promoter 135 bp upstream of tp-mglB is believed to direct mRNA synthesis for the operon. This is the first membrane protein-encoding operon of T. pallidum for which a putative function (glucose import) has been assigned. Furthermore, by analogy with E. coli MglB which interacts with the sensory transducer Trg to induce a chemotactic response, 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 with respect to T. pallidum survival, tissue dissemination, and sensory transduction during virulence expression.
梅毒螺旋体苍白亚种（T. pallidum）的一种38 kDa脂蛋白，先前被鉴定为大肠杆菌MglB的假定同源物[Becker等人（1994年），《感染与免疫》62卷，1381 - 1391页]。在本研究中，对梅毒螺旋体38 kDa脂蛋白基因相邻区域进行基因组步移，鉴定出三个相邻基因（tp - mglB [原tpp38]、tp - mglA和tp - mglC），它们似乎构成了梅毒螺旋体中的一个类mgl操纵子。与操纵子的第一个基因tp - mglB相对应的一个显著转录本由梅毒螺旋体合成，该基因编码碳水化合物受体，同时还合成了与整个梅毒螺旋体mgl操纵子相对应的丰度较低的转录本。据信，tp - mglB上游135 bp处的一个活性启动子指导该操纵子的mRNA合成。这是梅毒螺旋体第一个被赋予假定功能（葡萄糖转运）的膜蛋白编码操纵子。此外，通过与与感觉转导蛋白Trg相互作用以诱导趋化反应的大肠杆菌MglB进行类比，梅毒螺旋体也可能含有大肠杆菌Trg或其他甲基接受趋化蛋白的同源物。因此，梅毒螺旋体中mgl操纵子的存在可能对梅毒螺旋体在毒力表达过程中的存活、组织扩散和感觉转导具有重要意义。
