Mills D A, Manias D A, McKay L L, Dunny G M
Department of Microbiology, University of Minnesota, Minneapolis 55455-0312, USA.
J Bacteriol. 1997 Oct;179(19):6107-11. doi: 10.1128/jb.179.19.6107-6111.1997.
Ll.ltrB is a functional group II intron located within a gene (ltrB) encoding a conjugative relaxase essential for transfer of the lactococcal element pRSO1. In this work, the Ll.ltrB intron was shown to be an independent mobile element capable of inserting into an intronless allele of the ltrB gene. Ll.ltrB was not observed to insert into a deletion derivative of the ltrB gene in which the intron splice site was removed. In contrast, a second vector containing a 271-nucleotide segment of ltrB spanning the Ll.ltrB splice site was shown to be a proficient recipient of intron insertion. Efficient homing was observed in the absence of a functional host homologous recombination system. This work demonstrates that the Ll.ltrB intron is a novel site-specific mobile element in lactococci and that group II intron self-transfer is a mechanism for intron dissemination among bacteria.
Ll.ltrB是一个功能性II类内含子，位于编码对乳球菌元件pRSO1转移至关重要的接合松弛酶的基因（ltrB）内。在这项研究中，Ll.ltrB内含子被证明是一个独立的可移动元件，能够插入ltrB基因的无内含子等位基因中。未观察到Ll.ltrB插入去除了内含子剪接位点的ltrB基因缺失衍生物中。相反，含有跨越Ll.ltrB剪接位点的271个核苷酸的ltrB片段的第二个载体被证明是内含子插入的有效受体。在缺乏功能性宿主同源重组系统的情况下观察到了高效归巢。这项研究表明，Ll.ltrB内含子是乳球菌中一种新型的位点特异性可移动元件，并且II类内含子的自我转移是细菌内含子传播的一种机制。
