Chen J H, Hsu W B, Hwang J L
Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan 402, Republic of China
J Bacteriol. 1998 Oct;180(19):5279-83. doi: 10.1128/JB.180.19.5279-5283.1998.
Escherichia coli W3110 contains four types of IS1 elements in the chromosome. Using an insertion element entrapping system, we collected 116 IS1 plasmid insertion mutants, which resulted from a minimum of 26 independent IS1 insertion events. All of them had insertions of IS1 of the IS1A (IS1E and IS1G) type. Inspection of the transposase sequences of the four IS1 types and the IS1 of the resistance plasmid R100 showed that two amino acid residues, His-193 and Leu-217 of transposase, might contribute to differential transposability of IS1 elements in W3110. The two amino acid residues of the transposase in IS1A (IS1E and IS1G) were altered separately by site-directed mutagenesis, and each mutant was found to mediate transposition at a frequency about 30-fold lower than that of IS1A (IS1E and IS1G). Thus, the assumption that His-193 and Leu-217 of transposase contribute to differential transposability of IS1 elements in W3110 was confirmed.
大肠杆菌W3110的染色体中含有四种类型的IS1元件。利用插入元件捕获系统，我们收集了116个IS1质粒插入突变体，这些突变体至少源于26次独立的IS1插入事件。所有突变体均为IS1A（IS1E和IS1G）类型的IS1插入。对四种IS1类型以及抗性质粒R100的IS1的转座酶序列进行检查后发现，转座酶的两个氨基酸残基，即His-193和Leu-217，可能导致W3110中IS1元件转座能力的差异。通过定点诱变分别改变了IS1A（IS1E和IS1G）中转座酶的两个氨基酸残基，发现每个突变体介导转座的频率比IS1A（IS1E和IS1G）低约30倍。因此，转座酶的His-193和Leu-217导致W3110中IS1元件转座能力存在差异这一假设得到了证实。
