Maneewannakul S, Kathir P, Ippen-Ihler K
Department of Medical Microbiology and Immunology, Texas A&M University, College Station 77843.
J Mol Biol. 1992 May 20;225(2):299-311. doi: 10.1016/0022-2836(92)90923-8.
The product of the F plasmid transfer gene, traN, is thought to be required for the formation of stable mating aggregates during F-directed conjugation. By testing chimeric plasmids that express F transfer region segments for complementation of F lac traN mutant transfer, we mapped traN to the F transfer region between trbC and traF. Both protein and DNA sequence analysis determined the traN product to be a large, 66,000-Mr, polypeptide that undergoes signal sequence processing. The mature polypeptide was associated with outer membrane protein fractions, and a protease accessivity test confirmed that at least one portion of TraN is exposed on the cell surface. Our DNA sequence analysis also revealed that another gene, trbE, is located between traN and traF. The product of trbE was identified and shown to be a small, integral, inner membrane protein. The mating efficiency and pilus-specific phage susceptibility of a trbE::kan insertion mutant suggested that trbE is not essential for F transfer from Escherichia coli K-12 under standard mating conditions.
F质粒转移基因traN的产物被认为是F介导的接合过程中形成稳定交配聚集体所必需的。通过测试表达F转移区域片段的嵌合质粒对F lac traN突变体转移的互补作用，我们将traN定位到trbC和traF之间的F转移区域。蛋白质和DNA序列分析均确定traN产物是一种经过信号序列加工的66,000道尔顿的大型多肽。成熟多肽与外膜蛋白组分相关，蛋白酶可及性测试证实TraN的至少一部分暴露在细胞表面。我们的DNA序列分析还表明，另一个基因trbE位于traN和traF之间。trbE的产物已被鉴定并证明是一种小型的、整合的内膜蛋白。trbE::kan插入突变体的交配效率和菌毛特异性噬菌体敏感性表明，在标准交配条件下，trbE对于F从大肠杆菌K-12转移并非必需。
