Université de Toulouse, UPS, Laboratoire de Microbiologie et de Génétique Moléculaires, F-31000 Toulouse, France.
J Bacteriol. 2010 Feb;192(3):624-35. doi: 10.1128/JB.00986-09. Epub 2009 Nov 30.
The integrase of the temperate bacteriophage mv4 catalyzes site-specific recombination between the phage attP site and the host attB site during Lactobacillus delbrueckii lysogenization. The mv4 prophage is excised during the induction of lytic growth. Excisive site-specific recombination between the attR and attL sites is also catalyzed by the phage-encoded recombinase, but the directionality of the recombination is determined by a second phage-encoded protein, the recombination directionality factor (RDF). We have identified and functionally characterized the RDF involved in site-specific excision of the prophage genome. The mv4 RDF, (mv4)Xis, is encoded by the second gene of the early lytic operon. It is a basic protein of 56 amino acids. Electrophoretic mobility shift assays demonstrated that (mv4)Xis binds specifically to the attP and attR sites via two DNA-binding sites, introducing a bend into the DNA. In vitro experiments and in vivo recombination assays with plasmids in Escherichia coli and Lactobacillus plantarum demonstrated that (mv4)Xis is absolutely required for inter- or intramolecular recombination between the attR and attL sites. In contrast to the well-known phage site-specific recombination systems, the integrative recombination between the attP and attB sites seems not to be inhibited by the presence of (mv4)Xis.
温和噬菌体 mv4 的整合酶在德氏乳杆菌溶源化过程中催化噬菌体 attP 位点与宿主 attB 位点之间的特异性重组。mv4 原噬菌体在裂解生长的诱导过程中被切除。噬菌体编码的重组酶也催化 attR 和 attL 位点之间的切除特异性重组，但重组的方向性由第二个噬菌体编码的蛋白，即重组方向性因子（RDF）决定。我们已经鉴定并功能表征了参与原噬菌体基因组特异性切除的 RDF。mv4 的 RDF（mv4）Xis 由早期裂解操纵子的第二个基因编码。它是一种由 56 个氨基酸组成的碱性蛋白。电泳迁移率变动分析表明，（mv4）Xis 通过两个 DNA 结合位点特异性结合到 attP 和 attR 位点，使 DNA 产生弯曲。在大肠杆菌和植物乳杆菌中的质粒的体外实验和体内重组实验表明，（mv4）Xis 绝对需要 attR 和 attL 位点之间的分子内或分子间重组。与著名的噬菌体特异性重组系统不同，attP 和 attB 位点之间的整合性重组似乎不受（mv4）Xis 的存在抑制。
