Zähner D, Grebe T, Guenzi E, Krauss J, van der Linden M, Terhune K, Stock J B, Hakenbeck R
Max-Planck Institut für molekulare Genetik, Berlin, Germany.
Microb Drug Resist. 1996 Summer;2(2):187-91. doi: 10.1089/mdr.1996.2.187.
Laboratory mutants of Streptococcus pneumoniae resistant to either cefotaxime or piperacillin reveal defects in competence development independent of the selective beta-lactam. A resistance determinant ciaH encoding a putative histidine kinase of a two-component signal-transducing system that is also involved in competence regulation was recently identified in cefotaxime-resistant mutants. We show now that the CiaH protein can be phosphorylated by ATP in vitro, and that it also phosphorylates the cognate response regulator CiaR. The mutant C306 containing the CiaH mutation Thr-230-Pro is completely noncompetent. It does not release competence-inducing activity (competence factor) into the medium nor can such an activity be released from the cells. Competence in C306 cannot be induced upon addition of external competence factor, in contrast to the competence-defective piperacillin-resistant mutants P506 and P408. A novel resistance determinant cpoA specific for piperacillin was identified in piperacillin-resistant mutants. CpoA is responsible for the competence defect in P506 but not in P408. The results document a tight link between the action of beta-lactams and competence development in the pneumococcus and confirm that the two beta-lactams piperacillin and cefotaxime act via different primary targets.
对头孢噻肟或哌拉西林耐药的肺炎链球菌实验室突变体显示，其感受态发育存在缺陷，且与选择性β-内酰胺无关。最近在耐头孢噻肟的突变体中发现了一个耐药决定簇ciaH，它编码一个双组分信号转导系统的假定组氨酸激酶，该系统也参与感受态调节。我们现在表明，CiaH蛋白在体外可被ATP磷酸化，并且它还能磷酸化同源应答调节因子CiaR。含有CiaH突变Thr-230-Pro的突变体C306完全没有感受态。它不会向培养基中释放诱导感受态的活性物质（感受态因子），细胞也无法释放这种活性物质。与有感受态缺陷的耐哌拉西林突变体P506和P408不同，向C306中添加外部感受态因子不能诱导其产生感受态。在耐哌拉西林的突变体中发现了一个对哌拉西林特异的新耐药决定簇cpoA。CpoA导致P506出现感受态缺陷，但不导致P408出现感受态缺陷。这些结果证明了β-内酰胺的作用与肺炎链球菌感受态发育之间存在紧密联系，并证实了两种β-内酰胺哌拉西林和头孢噻肟通过不同的主要靶点发挥作用。
