Colombi D, Gomes S L
Departamento de Bioquimica, Instituto de Quimica, Universidade de Sao Paulo, Brazil.
J Bacteriol. 1997 May;179(10):3139-45. doi: 10.1128/jb.179.10.3139-3145.1997.
A Caulobacter crescentus alkB gene homolog was identified in a clone previously shown to contain the heat shock genes dnaK and dnaJ; the homolog is located upstream of dnaK and is transcribed in the opposite orientation. An analysis of the alkB gene has shown that the deduced amino acid sequence is that of a 21-kDa protein, which is 42% identical and 78% similar to Escherichia coli AlkB. Furthermore, an alkB-null mutant was constructed by gene disruption and was shown to be highly sensitive to the alkylating agent methyl methanesulfonate (MMS). However, the alkB gene of C. crescentus, unlike its E. coli counterpart, is not located downstream of the ada gene, and its transcription is not induced by alkylating agents. In addition, no acquired enhanced resistance to MMS toxicity by treatment with low MMS doses was observed, suggesting that no adaptive response occurs in C. crescentus. Nevertheless, transcription of the alkB gene is cell cycle controlled, with a pattern of expression similar to that of several Caulobacter genes involved in DNA replication.
在一个先前显示含有热休克基因dnaK和dnaJ的克隆中，鉴定出了一个新月柄杆菌alkB基因的同源物；该同源物位于dnaK上游，转录方向相反。对alkB基因的分析表明，推导的氨基酸序列是一个21 kDa蛋白质的序列，它与大肠杆菌AlkB的同一性为42%，相似性为78%。此外，通过基因破坏构建了一个alkB缺失突变体，结果表明该突变体对烷基化剂甲磺酸甲酯（MMS）高度敏感。然而，新月柄杆菌的alkB基因与其大肠杆菌对应物不同，它不位于ada基因下游，其转录也不会被烷基化剂诱导。此外，未观察到通过低剂量MMS处理获得对MMS毒性的增强抗性，这表明新月柄杆菌中不会发生适应性反应。尽管如此，alkB基因的转录受细胞周期控制，其表达模式与几个参与DNA复制的新月柄杆菌基因相似。
