噬菌体λ的质粒编码GamS功能对大肠杆菌recBC活性的选择性抑制

Selective inhibition of Escherichia coli recBC activities by plasmid-encoded GamS function of phage lambda.

作者信息

Friedman S A, Hays J B

出版信息

Gene. 1986;43(3):255-63. doi: 10.1016/0378-1119(86)90214-3.

Abstract

The gam locus of bacteriophage lambda encompasses two coding sequences with the same reading frame and translational stop, one corresponding to an Mr 11646 polypeptide (gamS gene), the other to an Mr 16349 polypeptide (gamL gene). A DNA segment encoding gamS but not gamL was placed under lambda pR promoter control (regulated by the cIts857-coded repressor) on a multicopy plasmid, and an insertion mutation (gamS201) was constructed. Expression of gamS+, but not gamS201, inhibited Escherichia coli RecBC nuclease in vivo; the criteria were inhibition of chromosomal DNA degradation after UV irradiation and plating of T4 gene 2- phages. The recB+ C+ bacteria expressing gamS+ were completely or partially similar to recC- mutants with respect to certain phenotypes: defective plating of phages P1 and P2, ability to plate (in a recA- background) lambda red- gam- phages, reduced resistance to UV irradiation, defective SOS induction, decreased colony-forming ability.

摘要

噬菌体λ的gam基因座包含两个具有相同阅读框和翻译终止密码子的编码序列，一个对应于Mr 11646多肽（gamS基因），另一个对应于Mr 16349多肽（gamL基因）。将编码gamS但不编码gamL的DNA片段置于多拷贝质粒上的λ pR启动子控制下（由cIts857编码的阻遏物调控），并构建了一个插入突变体（gamS201）。gamS+而非gamS201的表达在体内抑制了大肠杆菌RecBC核酸酶；其标准是抑制紫外线照射后染色体DNA的降解以及T4基因2噬菌体的平板接种。表达gamS+的recB+C+细菌在某些表型方面与recC-突变体完全或部分相似：噬菌体P1和P2的平板接种缺陷、（在recA-背景下）λ red-gam-噬菌体的平板接种能力、对紫外线照射的抗性降低、SOS诱导缺陷、菌落形成能力下降。