Nonconserved segment of the MutL protein from Escherichia coli K-12 and Salmonella typhimurium.
Nonconserved segment of the MutL protein from Escherichia coli K-12 and Salmonella typhimurium.
复制标题
来自大肠杆菌 K-12 和鼠伤寒沙门氏菌的 MutL 蛋白的非保守片段。
DOI：
10.1093/nar/20.9.2379
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发表时间：
1992
影响因子：
14.9
通讯作者：
Winkler,ME
中科院分区：
文献类型：
--
作者：
Tsui,HT;Mandavilli,BS;Winkler,ME
The mutL gene product is required for methyl-directed mismatch repair in vivo (1-3) and in vitro (4, 5), although its exact biochemical function is unclear (5). According to one recent model, MutL protein may function as an interface between the MutS protein, which binds to base-pair mismatches, and the MutH d (GATC) endonuclease (5). The mutL gene ofEscherichia coli K-12 and Salmonella typhimurium seems to be in a complex operon with at least two other genes (6-8). The upstream gene encodes a 47,000 dalton proteinof unknown function. The downstream gene is miaA, which encodes a tRNA modification enzyme, and the translation stop and start of mutL and miaA probably overlap (7). To understand the regulation of this complex locus, it was necessary to determine the DNA sequence of E. coli mutL and other potential upstream genes. Because E. coli MutL has been the subject of several biochemical studies (5), we wanted to make its deduced amino acid sequence available as soon as possible.Comparison of E. coli MutL with the previously published sequence of the S. typhimurium enzyme showed one noteworthy feature. The first 330 and last 189 amino acids of MutL from E. coli and S. typhimurium are generally highly conserved with no gaps and few nonidentical or nonsimilar amino acids. In contrast, the central region of the MutL protein (amino acids 331-425 relative to the E. coli sequence) consists of a mixture of conserved and nonconserved segments, including three distinct gaps (Fig. 1). In this regard, it is interesting that a recent comparison of the E. coli and S. typhimurium MutS proteins also revealed nonconserved segments, including gaps, at the middle of the protein, but highly conserved, nearly identical sequences at both ends (9). Moreover, when we compared other analogous protein pairs from E. coli and S. typhimurium, we found that such distinct internal gaps are relatively rare. Of 133 pairs available in the SwissProt database, approximately 94% contained no gaps or only one gap ofone or two amino acids. Besides MutL and MutS, only five other protein pairs (CheA, Dyr3, FliC, OmpA, and PhoQ) showed sizeable internal gaps. One speculation is that the nonconserved segments in MutL and MutS may represent hinge regions between different protein domains which interact with MutS and MutH or with DNA and MutL, respectively. As expected from previous studies, the E. coli MutL amino acid sequence reported here showed significant homology
