Watson M W, Clarke I N, Everson J S, Lambden P R
University Medical School, Southampton General Hospital, UK.
Microbiology (Reading). 1995 Oct;141 ( Pt 10):2489-97. doi: 10.1099/13500872-141-10-2489.
One of the critical developmental events during the unique intracellular life cycle of Chlamydiae is their differentiation from a metabolically active, replicative form or reticulate body (RB) to an infectious extracellular form of the organism (elementary body or EB). This process is characterized by the expression of two extraordinarily cysteine-rich envelope proteins of molecular masses 9 kDa and 60 kDa. We describe the molecular cloning and sequence determination of the 9 kDa cysteine-rich proteins (CrPs) of C. pneumoniae and C. psittaci. Comparison of these 9 kDa CrP amino acid sequences with those of C. trachomatis showed regions of structural variation and conservation. Transcription of the 9 kDa CrP genes occurred as both a monocistronic message and as a bicistronic message which included the 60 kDa CrP gene. Transcription of the 9 kDa and 60 kDa CrP genes was tightly linked to the chlamydial growth cycle with synthesis of their mRNAs and consequent translation of the 60 kDa CrPs occurring as RBs differentiated to form EBs. The maximal rate of transcription occurred late in the growth cycle from a single but highly conserved promoter which had close similarity with the Escherichia coli consensus promoter sequences. A stem and loop structure which could be involved in regulating translation of mRNA occurred in all three species between the transcriptional start point and the ribosome binding site. Although transcription is initiated from a single promoter in all three chlamydial species, transcriptional termination points for the monocistronic and bicistronic mRNAs differ in both number and position.
衣原体独特的细胞内生命周期中的一个关键发育事件是它们从代谢活跃的复制形式或网状体（RB）分化为该生物体的传染性细胞外形式（原体或EB）。这一过程的特征是表达两种分子量分别为9 kDa和60 kDa的异常富含半胱氨酸的包膜蛋白。我们描述了肺炎衣原体和鹦鹉热衣原体9 kDa富含半胱氨酸蛋白（CrP）的分子克隆和序列测定。将这些9 kDa CrP氨基酸序列与沙眼衣原体的序列进行比较，发现了结构变异和保守区域。9 kDa CrP基因的转录以单顺反子信息和双顺反子信息的形式发生，双顺反子信息包括60 kDa CrP基因。9 kDa和60 kDa CrP基因的转录与衣原体生长周期紧密相关，随着RB分化形成EB，它们的mRNA合成以及60 kDa CrP的后续翻译也随之发生。转录的最大速率发生在生长周期后期，从一个单一但高度保守的启动子开始，该启动子与大肠杆菌共有启动子序列高度相似。在所有三个物种中，转录起始点和核糖体结合位点之间都出现了一个可能参与调节mRNA翻译的茎环结构。尽管在所有三种衣原体物种中转录都从一个单一启动子开始，但单顺反子和双顺反子mRNA的转录终止点在数量和位置上都有所不同。
