Musatovova O, Alderete J F
Department of Microbiology, The University of Texas Health Science Center at San Antonio, 78284-7758, USA.
Microb Pathog. 1999 Aug;27(2):93-104. doi: 10.1006/mpat.1999.0281.
The prominent and phenotypically variable immunogenic protein of Trichomonas vaginalis, termed P270, is present in all isolates. Most, if not all, patients make antibody to the DREGRD epitope contained in the 333 bp tandemly repeating element (TRE). The complete sequence of p270 of a fresh clinical isolate was recently derived (Musatovova and Alderete, Microb Pathogen 1998; 24: 223-39). We hypothesized that the size polymorphisms of P270 were due to the varied number of TREs that comprise a large, central portion of the gene. In this study, we analysed the p270 coding regions of ten representative isolates. It was determined also that the sequence of the TRE of different p270 genes shared > or =99% identity, and individual TREs of the same p270 gene showed them to have identical nucleotide sequences, affirming the highly-conserved nature of this element within each gene. The coding regions upstream and downstream of the central TREs were then generated by PCR amplification using specific primers. The PCR products corresponding to the 5' and 3'-end coding, non-repeat sequences were then subjected to restriction analyses, and the regions were highly conserved for all p270 genes. The complete sequence of two p270 genes showed > or = 99% identity of amino acids at the N- and C-terminal regions of p270, further reinforcing that the reported polymorphisms in Mr of P270 is due to the varying number of TREs and, therefore, the size of the TRE domain. In support of this hypothesis and during these analyses, one isolate, T. vaginalis T016, was discovered which possessed a p270 gene with only one partial repeat unit. Importantly, and as with all other p270 genes, transcription of this single-repeat p270 gene in isolate T016 was confirmed. The start codon for the p270 T016 gene was preceded by the 12 nucleotide consensus Inr promoter-like sequence (TCATTTTTAATA) and possessed a putative transmembrane domain at the carboxy terminus.
阴道毛滴虫显著且表型多变的免疫原性蛋白，称为P270，存在于所有分离株中。大多数（即便不是全部）患者会产生针对333bp串联重复元件（TRE）中所含DREGRD表位的抗体。最近获得了一株新鲜临床分离株的p270完整序列（Musatovova和Alderete，《微生物病原体》1998年；24：223 - 39）。我们推测P270的大小多态性是由于构成该基因很大中央部分的TRE数量不同所致。在本研究中，我们分析了十个代表性分离株的p270编码区。还确定不同p270基因的TRE序列具有≥99%的同一性，并且同一p270基因的各个TRE显示它们具有相同的核苷酸序列，证实了该元件在每个基因内具有高度保守性。然后使用特异性引物通过PCR扩增产生中央TRE上下游的编码区。对应于5'和3'末端编码非重复序列的PCR产物随后进行限制性分析，并且这些区域在所有p270基因中高度保守。两个p270基因的完整序列显示在p270的N端和C端区域氨基酸同一性≥99%，进一步证明所报道的P270相对分子质量多态性是由于TRE数量不同，因此是TRE结构域的大小不同所致。为支持这一假设并在这些分析过程中，发现了一株阴道毛滴虫T016分离株，其p270基因仅具有一个部分重复单元。重要的是，与所有其他p270基因一样，证实了该单重复p270基因在分离株T016中进行转录。p270 T016基因的起始密码子之前有12个核苷酸的共有Inr启动子样序列（TCATTTTTAATA），并且在羧基末端具有一个推定的跨膜结构域。
