Identification of a RecA homolog (RecA(LP)) on the conjugative lactococcal phage resistance plasmid pNP40: Evidence of a role for chromosomally encoded RecA(L) in abortive infection
Identification of a RecA homolog (RecA(LP)) on the conjugative lactococcal phage resistance plasmid pNP40: Evidence of a role for chromosomally encoded RecA(L) in abortive infection
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DOI：
10.1128/aem.63.4.1244-1251.1997
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发表时间：
1997-04-01
影响因子：
4.4
通讯作者：
Fitzgerald, GF
中科院分区：
文献类型：
--
作者：
Garvey, P;Rince, A;Fitzgerald, GF
两种噬菌体抗性机制AbiE和AbiF的决定子在乳球菌质粒pNP 40上被大约3，300个核苷酸分开（P. Garvey，G. F. Fitzgerald和C. Hill，应用环境，微生物学，61：4321-4328，1995），间插区的DNA序列分析导致鉴定了两个开放阅读框（ORF），其以与Abi决定簇相反的方向转录，这些ORF之一编码recA同源物第二个ORF（orfU）与SOS反应的umuC基因具有同源性，对许多乳球菌菌株的分析证实了recA（LP）样序列在至少两种其他乳球菌菌株中的存在，recA和umuC同源物的接近表明在由Abi决定簇编码的噬菌体抗性中可能起作用，然而，没有证据表明ORF在AbiE或AbiF表达中的功能。recA（LP）基因也不能恢复recA缺陷型乳球菌菌株VEL 1122中对丝裂霉素的抗性。有趣的是，显示了染色体编码的recA对于AbiF表型的完全表达是必需的，证实了RecA在这种流产感染系统中的作用。
The determinants for two bacteriophage resistance mechanisms, AbiE and AbiF, are separated by approximately 3,300 nucleotides on the lactococcal plasmid pNP40 (P. Garvey, G. F. Fitzgerald, and C. Hill, Appl. Environ, Microbiol, 61:4321-4328, 1995), DNA sequence analysis of the intervening region led to the identification of two open reading frames (ORFs) which are transcribed in the opposite direction to the Abi determinants, One of these ORFs encodes a recA homolog (designated recA(LP)), This is the first report of a recA-like determinant located to a plasmid, The second ORF (orfU) shares homology with the umuC gene of the SOS response, Analysis of a number of lactococcal strains confirmed the presence of recA(LP)-like sequences in at least two other lactococcal strains, The proximity of the recA and umuC homologs suggested a possible role in the phage resistance encoded by the Abi determinants, However, no evidence was obtained to demonstrate a function for either ORF in the expression of either AbiE or AbiF, Nor could the recA(LP) gene restore resistance to mitomycin in a recA-deficient lactococcal strain, VEL1122, Interestingly, it was shown that the chromosomally encoded recA is necessary for complete expression of the AbiF phenotype, confirming a role for RecA in this abortive infection system.