Identification and characterization of bicistronic speB and prsA gene expression in the group A streptococcus
Identification and characterization of bicistronic speB and prsA gene expression in the group A streptococcus
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DOI：
10.1128/jb.01059-06
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发表时间：
2006-11-01
影响因子：
3.2
通讯作者：
Stevens, Dennis L.
中科院分区：
文献类型：
--
作者：
Ma, Yongsheng;Bryant, Amy E.;Stevens, Dennis L.
严重的侵袭性A群链球菌感染在世界范围内再次出现，细胞外毒素，包括链球菌热原外毒素B (SpeB)，与发病机制有关。SpeB的遗传调控尚不完全清楚，而将原蛋白转化为酶活性形式的机制也尚未明确确立。目前的研究表明，编码SpeB （SpeB）和肽基脯氨酸异构酶（prsA）的基因构成了一个操纵子，其转录由SpeB上游的两个启动子启动。此外，speB-prsA操纵子被转录为双子mRNA。这一发现与普遍接受的观点相反，即speB仅作为单顺反子基因转录。此外，prsA有自己的启动子，从这个启动子开始转录在早期log期，在speB转录之前。prsA的基因组破坏降低了酶活性Spell的产生，但没有降低pro-SpeB酶原的水平。综上所述，这些结果表明，prsA是生产完全成熟的酶活性SpeB所必需的。
Severe, invasive group A streptococcal infections have reemerged worldwide, and extracellular toxins, including streptococcal pyrogenic exotoxin B (SpeB), have been implicated in pathogenesis. The genetic regulation of SpeB is not fully understood, and the mechanisms involved in the processing of the protoxin to its enzymatically active form have not been definitively established. The present work demonstrated that the genes encoding SpeB (speB) and a peptidyl-prolyl isomerase (prsA) constitute an operon with transcription initiated from two promoters upstream of speB. Further, the speB-prsA operon was transcribed as a bicistronic mRNA. This finding is in contrast to the generally accepted notion that speB is transcribed only as a monocistronic gene. In addition, prsA has its own promoter, and transcription from this promoter starts in early log phase, prior to the transcription of speB. Genomic disruption of prsA decreased the production of enzymatically active Spell but not the level of the pro-SpeB zymogen. Taken together, these results demonstrate that prsA is required for production of fully mature, enzymatically active SpeB.