Mo Y Y, Cianciotto N P, Mallavia L P
Department of Microbiology, Washington State University, Pullman 99164-4233, USA.
Microbiology (Reading). 1995 Nov;141 ( Pt 11):2861-71. doi: 10.1099/13500872-141-11-2861.
The gene encoding a protein that reacted with antibodies specific for Legionella pneumophila macrophage infectivity potentiator (LpMip) was cloned from Coxiella burnetii, the obligate intracellular rickettsia that causes Q fever in humans. Nucleotide sequencing analysis revealed an ORF encoding a gene product of 230 amino acids with a molecular mass of 25.5 kDa and a predicted pI of 10.7. The predicted amino acid sequence from the ORF shows similarity with Mip/Mip-like proteins of Legionella (46%) and Chlamydia (30%). Moreover, like LpMip, the amino acid sequence of the C terminus of this protein has over 35% identity to prokaryotic and eukaryotic FK506-binding proteins (FKBPs) that belong to a superfamily of immunophilins and are peptidyl-prolyl cis-trans isomerases (PPIases). When overproduced in Escherichia coli, the C. burnetii protein also exhibited PPIase activity. Taken together, these results demonstrate that C. burnetii encodes a Mip analogue (CbMip). A putative leader peptide at the N terminus of CbMip was detected by computer analysis. Furthermore, TnphoA mutagenesis demonstrated that in E. coli CbMip was secreted. In view of the role of Mip/Mip-like proteins in the pathogenesis of Legionella and Chlamydia, CbMip may be a C. burnetii virulence factor.
从引起人类Q热的专性细胞内立克次氏体——伯纳特柯克斯体中克隆出了一个基因，该基因编码一种能与嗜肺军团菌巨噬细胞感染增强因子（LpMip）特异性抗体发生反应的蛋白质。核苷酸序列分析显示，一个开放阅读框（ORF）编码一个由230个氨基酸组成的基因产物，分子量为25.5 kDa，预测的等电点为10.7。该ORF预测的氨基酸序列与军团菌（46%）和衣原体（30%）的Mip/Mip样蛋白具有相似性。此外，与LpMip一样，该蛋白C末端的氨基酸序列与属于免疫亲和素超家族且为肽基脯氨酰顺反异构酶（PPIase）的原核和真核FK506结合蛋白（FKBP）有超过35%的同一性。当在大肠杆菌中过量表达时，伯纳特柯克斯体蛋白也表现出PPIase活性。综上所述，这些结果表明伯纳特柯克斯体编码一种Mip类似物（CbMip）。通过计算机分析在CbMip的N末端检测到一个推定的前导肽。此外，TnphoA诱变表明在大肠杆菌中CbMip是分泌型的。鉴于Mip/Mip样蛋白在军团菌和衣原体发病机制中的作用，CbMip可能是伯纳特柯克斯体的一种毒力因子。
