GENETIC AND SEQUENCE ORGANIZATION OF THE MCRBC LOCUS OF ESCHERICHIA-COLI K-12
GENETIC AND SEQUENCE ORGANIZATION OF THE MCRBC LOCUS OF ESCHERICHIA-COLI K-12
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DOI：
10.1128/jb.172.9.4888-4900.1990
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发表时间：
1990-09-01
影响因子：
3.2
通讯作者：
RALEIGH, EA
中科院分区：
文献类型：
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作者：
DILA, D;SUTHERLAND, E;RALEIGH, EA
大肠杆菌K-12的mcrB（rglB）基因座介导胞嘧啶修饰的DNA的序列特异性限制。遗传和序列分析表明，该位点实际上包含两个基因，mcrB和mcrC。我们在这里表明，在体内，McrC修改McrB限制的特异性，通过扩大范围的修改序列的限制。也就是说，对McrB（+）依赖性限制敏感的序列可以分为两组：一些含有5-甲基胞嘧啶的修饰序列即使在McrC-时也被McrB+细胞限制，但大多数这样的序列在体内仅被McrB+ McrC+细胞限制。仅受McrB+C+限制的序列包括含有5-羟甲基胞嘧啶的T偶噬菌体（该噬菌体的限制是RglB+表型）、含有N4-甲基胞嘧啶的一些序列和含有5-甲基胞嘧啶的一些序列。该序列编码54（McrB）和42（McrC）千道尔顿的两种多肽，而体外翻译产生约29和约49（McrB）以及约38和约40（McrC）千道尔顿的四种产物。McrB多肽序列含有潜在的GTP结合基序，因此该蛋白质可能与核苷酸辅因子结合。推导的McrC多肽是有点碱性的，可以结合到DNA上，这与其作为McrB特异性调节剂的遗传活性一致。在核苷酸序列水平上，mcrBC的G+C含量对于E.这表明这些基因可能是最近在物种进化过程中获得的。
The mcrB (rglB) locus of Escherichia coli K-12 mediates sequence-specific restriction of cytosine-modified DNA. Genetic and sequence analysis shows that the locus actually comprises two genes, mcrB and mcrC. We show here that in vivo, McrC modifies the specificity of McrB restriction by expanding the range of modified sequences restricted. That is, the sequences sensitive to McrB(+)-dependent restriction can be divided into two sets: some modified sequences containing 5-methylcytosine are restricted by McrB+ cells even when McrC-, but most such sequences are restricted in vivo only by McrB+ McrC+ cells. The sequences restricted only by McrB+C+ include T-even bacteriophage containing 5-hydroxymethylcytosine (restriction of this phage is the RglB+ phenotype), some sequences containing N4-methylcytosine, and some sequences containing 5-methylcytosine. The sequence codes for two polypeptides of 54 (McrB) and 42 (McrC) kilodaltons, whereas in vitro translation yields four products, of approximately 29 and approximately 49 (McrB) and of approximately 38 and approximately 40 (McrC) kilodaltons. The McrB polypeptide sequence contains a potential GTP-binding motif, so this protein presumably binds the nucleotide cofactor. The deduced McrC polypeptide is somewhat basic and may bind to DNA, consistent with its genetic activity as a modulator of the specificity of McrB. At the nucleotide sequence level, the G+C content of mcrBC is very low for E. coli, suggesting that the genes may have been acquired recently during the evolution of the species.