Ahlawat Sarita, Morrison Donald A
LMB Room 4150, 900 South Ashland Ave., Chicago, IL 60607, USA.
J Bacteriol. 2009 Apr;191(8):2894-8. doi: 10.1128/JB.01715-08. Epub 2009 Feb 13.
Bacterial proteins that are abnormally truncated due to incomplete mRNA or the presence of rare codons are extended by an SsrA tag during ribosome rescue in a trans-translation process important for maintaining protein quality. In Escherichia coli, the SsrA-tagged proteins become the target of the Tsp, Lon, FtsH, ClpXP, and ClpAP proteases. Here we show that degradation of model SsrA-tagged proteins in Streptococcus pneumoniae depends primarily or exclusively on ClpXP in vivo. In addition, we show the E. coli SsrA tag is also a target of S. pneumoniae ClpXP in vivo, even though the N-terminal portions of the tags differ significantly between the two species, suggesting there may be no adaptor protein for SsrA in S. pneumoniae.
由于mRNA不完整或存在稀有密码子而异常截短的细菌蛋白质，在核糖体拯救过程中通过SsrA标签进行延伸，这一过程对于维持蛋白质质量非常重要，称为反式翻译。在大肠杆菌中，带有SsrA标签的蛋白质成为Tsp、Lon、FtsH、ClpXP和ClpAP蛋白酶的作用靶点。在这里，我们表明，在体内，肺炎链球菌中模型SsrA标签蛋白的降解主要或完全依赖于ClpXP。此外，我们还表明，大肠杆菌的SsrA标签在体内也是肺炎链球菌ClpXP的作用靶点，尽管两种细菌标签的N端部分存在显著差异，这表明肺炎链球菌中可能不存在SsrA的衔接蛋白。
