GENE-19 OF PLASMID-R1 IS REQUIRED FOR BOTH EFFICIENT CONJUGATIVE DNA TRANSFER AND BACTERIOPHAGE-R17 INFECTION
GENE-19 OF PLASMID-R1 IS REQUIRED FOR BOTH EFFICIENT CONJUGATIVE DNA TRANSFER AND BACTERIOPHAGE-R17 INFECTION
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DOI：
10.1128/jb.177.15.4279-4288.1995
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发表时间：
1995-08-01
影响因子：
3.2
通讯作者：
HOGENAUER, G
中科院分区：
文献类型：
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作者：
BAYER, M;EFERL, R;HOGENAUER, G
F样质粒需要许多基因用于接合，包括tra操纵子基因和位于tra操纵子外部的基因traM和traJ。我们现在确定，在“前导区”的基因，基因19，在接合和RNA噬菌体感染过程中提供了重要的功能。通过引入两个非极性终止密码子使质粒R1-16上的基因19突变失活，导致接合频率降低10倍。此外，用雄性特异性噬菌体R17进行的感染研究表明，该噬菌体不能在携带具有基因19缺陷拷贝的R1-16质粒的大肠杆菌中形成清晰的噬斑。被噬菌体R17感染的细胞总数减少了10倍。通过引入编码野生型蛋白的基因19等位基因，可以反式补充由缺陷基因19引起的接合和感染减弱的表型。正常表型的恢复也可以通过导入由无关的IncI质粒R64编码的pilT基因来实现。我们的功能研究和相似性的蛋白质19编码的其他DNA转移系统的蛋白质，以及在所有这些蛋白质中的保守基序的存在（指示推定的溶菌酶活性）表明，蛋白质19的质粒R1促进通过的DNA在接合和进入的RNA在噬菌体感染。
F-like plasmids require a number of genes for conjugation, including tra operon genes and genes traM and traJ which lie outside the tra operon. We now establish that a gene in the ''leading region,'' gene 19, provides an important function during conjugation and RNA phage infection. Mutational inactivation of gene 19 on plasmid R1-16 by introduction of two nonpolar stop codons results in a 10-fold decrease in the conjugation frequency. Furthermore, infection studies with the male-specific bacteriophage R17 revealed that the phage is not able to form clear plaques in Escherichia coli tells carrying an R1-16 plasmid with the defective copy of gene 19. The total number of cells infected by phage R17 is reduced by a factor of 10. Both the conjugation- and infection-attenuated phenotypes caused by the defective gene 19 can be complemented in trans by introducing gene 19 alleles encoding the wild-type protein. Restoration of the normal phenotypes is also possible by introduction of the pilT gene encoded by the unrelated IncI plasmid R64. Our functional studies and similarities of protein 19 to proteins encoded by other DNA transfer systems, as well as the presence of a conserved motif in all of these proteins (indicative for a putative muramidase activity) suggest that protein 19 of plasmid R1 facilitates the passage of DNA during conjugation and entry of RNA during phage infection.