Laine M J, Zhang Y P, Metzler M C
Department of Biology, University of Turku, Finland.
Plasmid. 1994 Nov;32(3):270-9. doi: 10.1006/plas.1994.1066.
We describe here a repetitive chromosomal element, which appears to be an insertion sequence, isolated from Clavibacter xyli subsp. cynodontis, a gram-positive plant-associated bacterium. The element, IS1237, is 905 bp in size, is bounded by 19-bp perfect inverted repeats and 3-bp direct repeats, and appears at least 16 times in the genome. It contains three open reading frames which show similarity to open reading frames from various other insertion sequences. We have found that there are two groups of related mobile elements: one in which two open reading frames are read separately and the other in which these two open reading frames are fused together to give one predicted protein product. Using one of these open reading frames to search amino acid sequence databases, we found two instances in which similar reading frames flank genes carried on plasmids. We believe therefore that these plasmid-borne genes may be parts of previously unidentified mobile elements. For IS1237, a frameshift in two of the open reading frames and a stop codon in the third may indicate that this particular copy of the element is no longer active in transposition. The similarity of IS1237 to other elements from both gram-negative and gram-positive bacteria provides further evidence that mobile elements have been transferred between these two bacterial groups.
我们在此描述一种重复染色体元件，它似乎是一个插入序列，从革兰氏阳性植物相关细菌——栖木杆菌嗜犬亚种中分离得到。该元件IS1237大小为905 bp，由19 bp的完美反向重复序列和3 bp的正向重复序列界定，在基因组中至少出现16次。它包含三个开放阅读框，与其他各种插入序列的开放阅读框具有相似性。我们发现有两组相关的移动元件：一组中两个开放阅读框分别被读取，另一组中这两个开放阅读框融合在一起产生一个预测的蛋白质产物。利用其中一个开放阅读框搜索氨基酸序列数据库，我们发现有两个实例，其中类似的阅读框位于质粒携带的基因两侧。因此我们认为，这些质粒携带的基因可能是以前未鉴定的移动元件组成部分。对于IS1237，其中两个开放阅读框发生移码，第三个出现终止密码子，这可能表明该元件的这个特定拷贝在转座中不再活跃。IS1237与革兰氏阴性和革兰氏阳性细菌的其他元件的相似性进一步证明移动元件已在这两个细菌类群之间转移。
