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Search for pathogenic factor in Rickettsia tsutsupamushi.

寻找恙虫病立克次体的致病因子。

基本信息

批准号：
63480155
负责人：
TAMURA Akira
金额：
$ 2.75万
依托单位：
Nigata University of Phermacy and Applied Life Sciences
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1990
项目状态：
已结题

项目摘要

There are several antigenic variants in Rickettsia tsutsugamushi. This antigenic variant is due to the antigenicities of 56-kilodalton(K)protein located on the rickettsial surface. We found recently that the virulence of individual strain to mice relates to the antigenic type of rickettsiae. This result suggests that the 56K protein may decide the virulence of this rickettsia. Therefore we analyzed, in this study, the molecular structure of 56K proteins from 3 virulent strains of Gilliam, Karp, and Kato, and 3 avirulent strains of Shimokoshi, Kawasaki, and Kuroki, by biochemical and gene-cloning methods, and compared the differences of the molecular structure among the strains. The results obtained are summarized as follows. (1)Promoter sequences and ribosome-binding Mite were deduced in the 5'-side flanking regions of cloned genes, of which the sequences are similar with the consensus and Shine-Dalgarno sequences in Escherichia coli, respectively. (2)Signal peptide composed of 22-amino acids was observed at the N-terminal side of the deduced amino acid sequences from all the six strains. (3)In the 56K protein molecules, 4 variable domains showing remarkable variations of amino acid sequences among the strains were recognized. (4)Hydrophobic and hydrophilic regions appeared alternatively in the molecules, showing typical properties of membrane protein. All the 4 variable domains located in the hydrophilic regions, suggesting that these domains are exposed on the surface of rickettsiae and antigenic site(epitope)may exist in these areas. (5)A hairpin loop structure was seen at the 3'-side flanking region of the gene about 20 bp downstream from the stop codon except the case of Kawasaki strain. (6)The variations of amino acid sequences among the strains were larger and more complex than we expected. To identify the sequence which relates to the virulence of the rickettsia, more detail studies on this protein are required in future.

恙虫病立克次体中有几种抗原变异体。这种抗原性变异是由于位于立克次体表面的56千道尔顿(K)蛋白的抗原性。我们最近发现，单个菌株对小鼠的毒力与立克次体的抗原型有关。这一结果表明，56K蛋白可能决定了立克次体的毒力。因此，本研究采用生化和基因克隆的方法，分析了Gilliam、Karp和Kato 3个强毒菌株和Shimokoshi、Kawasaki、Kuroki 3个无毒菌株的56K蛋白的分子结构，并比较了不同菌株之间的分子结构差异。所获得的结果总结如下。(1)在克隆基因的5‘侧翼区推导出启动子序列和核糖体结合螨序列，其序列分别与大肠杆菌中的Consensus序列和Shine-Dalgarno序列相似。(2)在推导的氨基酸序列的N末端，均观察到由22个氨基酸组成的信号肽。(3)在56K蛋白分子中，发现了4个氨基酸序列差异显著的可变区。(4)分子中疏水和亲水区域交替出现，呈现典型的膜蛋白性质。4个可变区均位于亲水性区域，提示这些区域暴露在立克次体表面，这些区域可能存在抗原位点(表位)。(5)除川崎株外，该基因3‘侧翼区在终止密码子下游约20bp处有发夹状结构。(6)菌株间氨基酸序列的变异比我们预想的更大、更复杂。为了确定与立克次体毒力相关的序列，未来需要对该蛋白进行更详细的研究。