Kim Su-Nam, Bae Yong-Goo, Rhee Dong-Kwon
KIST Gangneung Institute, Gangneung, Korea.
Arch Pharm Res. 2008 Apr;31(4):462-7. doi: 10.1007/s12272-001-1179-4. Epub 2008 May 1.
The dnaK and groE operons in Streptococcus pneumoniae are repressed by HrcA in the presence of Ca(++). However, it is unclear how HrcA and Ca(++) regulate the dnaK and groE operons. This study examined the dual regulation of the dnaK and groE operons in S. pneumoniae by HrcA and Ca(++). At 30 degrees C, the hrcA mutant showed a constitutively higher level of dnaK expression at both the protein and mRNA levels than that of the wild type whereas the level of groEL expression was relatively unchanged. On the other hand, the levels of both dnaK and groEL transcripts were increased after heat shock but the hrcA mutant was not sensitive to heat shock. Immunoblot analysis of the cells pretreated with the Ca(++) chelator, BAPTA-AM, revealed the induction of HrcA and GroEL at both 30 degrees C and 42 degrees C. However, at longer preincubation time with BAPTA-AM, GroEL was further induced but the level of HrcA decreased suggesting that Ca(++) regulates the dnaK and groE operons differently. Overall, Ca(++) and HrcA differentially regulate the transcription of the dnaK and groE operons in S. pneumoniae. These results are expected to contribute to resolving the relationship between DnaK/GroEL expression and the pathogenesis in S. pneumoniae.
在肺炎链球菌中，dnaK和groE操纵子在有Ca(++)存在时受HrcA抑制。然而，尚不清楚HrcA和Ca(++)如何调节dnaK和groE操纵子。本研究检测了肺炎链球菌中HrcA和Ca(++)对dnaK和groE操纵子的双重调控。在30℃时，hrcA突变体在蛋白质和mRNA水平上的dnaK表达水平均比野生型持续更高，而groEL表达水平相对不变。另一方面，热休克后dnaK和groEL转录本水平均升高，但hrcA突变体对热休克不敏感。用Ca(++)螯合剂BAPTA-AM预处理细胞的免疫印迹分析显示，在30℃和42℃时HrcA和GroEL均被诱导。然而，用BAPTA-AM预孵育较长时间后，GroEL进一步被诱导，但HrcA水平下降，表明Ca(++)对dnaK和groE操纵子的调节方式不同。总体而言，Ca(++)和HrcA对肺炎链球菌中dnaK和groE操纵子的转录有不同调节作用。这些结果有望有助于解析肺炎链球菌中DnaK/GroEL表达与发病机制之间的关系。
