Penfold S S, Usher K, Frost L S
Department of Microbiology, University of Alberta, Edmonton, Canada.
J Bacteriol. 1994 Apr;176(7):1924-31. doi: 10.1128/jb.176.7.1924-1931.1994.
The sequence of traK gene of the F sex factor of Escherichia coli is presented; the traK gene product is predicted to be a protein of 25,627 Da with a signal sequence of 21 amino acids to give a mature protein of 23,307 Da. The traK4 mutation is an extremely polar mutation in the F plasmid that affects F pilus synthesis and plasmid transfer. traK genes carrying the traK4 mutation and a nonpolar mutation traK105 were cloned, sequenced, and identified as an amber nonsense and a frameshift mutation, respectively. The traK4 mutation occurred within one predicted rho-dependent transcription termination element (TTE) and immediately upstream of another, while the traK105 mutation occurred after the two potential TTEs within the traK gene. S1 nuclease protection analysis and Northern (RNA) blot analysis were used to confirm that the traK4 mutation, but not the traK105 mutation, caused premature termination of transcription. Computer analysis of the F transfer region suggested the presence of TTE motifs at regular intervals throughout the 33.4-kb sequence.
本文给出了大肠杆菌F性因子traK基因的序列；预测traK基因产物是一种分子量为25,627 Da的蛋白质，带有一个21个氨基酸的信号序列，产生一个成熟蛋白质，分子量为23,307 Da。traK4突变是F质粒中的一个极端极性突变，影响F菌毛合成和质粒转移。克隆、测序了携带traK4突变的traK基因和一个非极性突变traK105，并分别鉴定为琥珀色无义突变和移码突变。traK4突变发生在一个预测的rho依赖性转录终止元件（TTE）内，紧挨着另一个TTE的上游，而traK105突变发生在traK基因内两个潜在TTE之后。用S1核酸酶保护分析和Northern（RNA）印迹分析来证实traK4突变而非traK105突变导致转录提前终止。对F转移区域的计算机分析表明，在整个33.4 kb序列中，TTE基序有规律地间隔出现。
