Alegre M T, Cournoyer B, Mesas J M, Guérineau M, Normand P, Pernodet J L
Laboratoire de Microbiologie des Sols, URA CNRS 1450, Université Claude Bernard-Lyon I, Villeurbanne, France.
Appl Environ Microbiol. 1994 Dec;60(12):4279-83. doi: 10.1128/aem.60.12.4279-4283.1994.
pSAM2 is a conjugative Streptomyces ambofaciens mobile genetic element that can transfer and integrate site specifically in the genome. The chromosomal attachment site (attB) for pSAM2 site-specific recombination for two Frankia species was analyzed. It overlaps putative proline tRNA genes having a 3'-terminal CCA sequence, an uncommon feature among actinomycetes. pSAM2 is able to integrate into a cloned Frankia attB site harbored in Streptomyces lividans. The integration event removes the 3'-terminal CCA sequence and introduces a single nucleotide difference in the T psi C loop of the putative Frankia tRNA(Pro) gene. Major differences between the attP sequence from pSAM2 and the Frankia attB sequence restrict the identity segment to a 43-bp-long region. Only one mismatch is found between these well-conserved att segments. This nucleotide substitution makes a BstBI recognition site in Frankia attB and was used to localize the recombination site in a 25-bp region going from the anticodon to the T psi C loop of the tRNA(Pro) sequence. Integration of pSAM2 into the Frankia attB site is the first step toward introduction of pSAM2 derivatives into Frankia spp.
pSAM2是一种可接合转移的嗜油链霉菌移动遗传元件，能够在基因组中进行位点特异性转移和整合。分析了两种弗兰克氏菌属物种中pSAM2位点特异性重组的染色体附着位点（attB）。它与具有3'-末端CCA序列的假定脯氨酸tRNA基因重叠，这在放线菌中是一个不常见的特征。pSAM2能够整合到淡紫链霉菌中携带的克隆弗兰克氏菌attB位点。整合事件去除了3'-末端CCA序列，并在假定的弗兰克氏菌tRNA（Pro）基因的T psi C环中引入了一个单核苷酸差异。pSAM2的attP序列与弗兰克氏菌attB序列之间的主要差异将同源区段限制在一个43bp长的区域。在这些高度保守的att区段之间仅发现一个错配。这种核苷酸取代在弗兰克氏菌attB中产生了一个BstBI识别位点，并用于将重组位点定位在从反密码子到tRNA（Pro）序列的T psi C环的25bp区域内。pSAM2整合到弗兰克氏菌attB位点是将pSAM2衍生物引入弗兰克氏菌属的第一步。
