Lombardo M J, Rosenberg S M
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
J Bacteriol. 2000 Nov;182(22):6287-91. doi: 10.1128/JB.182.22.6287-6291.2000.
The radC102 mutation causes mild UV and X-ray sensitivity and was mapped previously to near pyrE and recG at 82 min on the Escherichia coli chromosome (I. Felzenszwalb, N. J. Sargentini, and K. C. Smith, Radiat. Res. 97:615-625, 1984). We report that radC102 has two striking phenotypes characteristic of recG mutations. First, it causes dramatically increased RecA-dependent mutation in a stationary-phase mutation assay. Second, it causes extreme UV sensitivity in combination with ruv mutations affecting the RuvABC Holliday junction resolution system. DNA sequencing of the radC and recG genes in radC102 strains revealed that the radC102 mutation creates a stop codon in recG that is predicted to truncate the RecG protein at 410 of 603 amino acids. A low-copy-number plasmid carrying the radC(+) gene did not affect the UV sensitivity of a wild-type strain, a radC102 strain, or a recG258::Tn10mini-kan strain. We conclude that radC102 is an allele of recG and that the function of the RadC protein remains to be determined.
radC102突变导致对紫外线和X射线轻度敏感，此前已定位到大肠杆菌染色体上82分钟处靠近pyrE和recG的位置（I. Felzenszwalb、N. J. Sargentini和K. C. Smith，《辐射研究》97:615 - 625，1984年）。我们报告称，radC102具有recG突变的两个显著表型特征。首先，在稳定期突变试验中，它导致RecA依赖性突变显著增加。其次，它与影响RuvABC霍利迪连接点解离系统的ruv突变相结合时，会导致对紫外线极度敏感。对radC102菌株中radC和recG基因进行DNA测序发现，radC102突变在recG中产生一个终止密码子，预计会使RecG蛋白在603个氨基酸中的第410位处截短。携带radC(+)基因的低拷贝数质粒不影响野生型菌株、radC102菌株或recG258::Tn10迷你卡那菌株的紫外线敏感性。我们得出结论，radC102是recG的一个等位基因，RadC蛋白的功能仍有待确定。
