Novick R P, Adler G K, Majumder S, Khan S A, Carleton S, Rosenblum W D, Iordanescu S
Proc Natl Acad Sci U S A. 1982 Jul;79(13):4108-12. doi: 10.1073/pnas.79.13.4108.
pT181 is a 4.4-kilobase plasmid from Staphylococcus aureus specifying tetracycline resistance and present in about 20 copies per cell. The existence of a diffusible pT181 product required for plasmid replication has been proposed on the basis of trans-complementable thermosensitive mutants defective in plasmid maintenance (phenotype Tsr). In this report, the Tsr mutants are shown to have primary replication defects, and the genetic complementation data are confirmed biochemically. All of five mutations are in a single cistron, the repC cistron; interruption of the plasmid DNA molecule at any of three neighboring restriction sites inactivates repC function. Analysis of the DNA sequence in this region reveals an open reading frame of 939 base pairs which encodes the repC product, a 313-amino acid protein. pT181 replication has been demonstrated in cell-free extracts to require specifically a pT181-coded protein of approximately the same size, and it is proposed that this protein is, indeed, the repC product. Preliminary evidence is discussed suggesting that the pT181 replication rate is controlled at the level of synthesis of the repC protein.
pT181是一种来自金黄色葡萄球菌的4.4千碱基质粒，它赋予四环素抗性，每个细胞中约有20个拷贝。基于在质粒维持方面有缺陷的可转互补温度敏感突变体（表型Tsr），有人提出存在一种质粒复制所需的可扩散pT181产物。在本报告中，Tsr突变体被证明存在初级复制缺陷，并且遗传互补数据得到了生化证实。五个突变全部位于一个单一顺反子，即repC顺反子；在三个相邻限制位点中的任何一个处中断质粒DNA分子都会使repC功能失活。对该区域DNA序列的分析揭示了一个939个碱基对的开放阅读框，它编码repC产物，一种313个氨基酸的蛋白质。已经在无细胞提取物中证明pT181复制特别需要一种大小大致相同的pT181编码蛋白，并且有人提出这种蛋白确实就是repC产物。文中讨论了初步证据，表明pT181复制速率在repC蛋白的合成水平受到控制。
