Ludwig B, Rahfeld J, Schmidt B, Mann K, Wintermeyer E, Fischer G, Hacker J
Institut für Molekulare Infektionsbiologie, Univ. Würzburg, FRG.
FEMS Microbiol Lett. 1994 May 1;118(1-2):23-30. doi: 10.1111/j.1574-6968.1994.tb06798.x.
The Mip ('macrophage infectivity potentiator') protein of Legionella pneumophila has been shown to be an essential virulence factor, exhibiting peptidyl-prolyl cis/trans isomerase (PPIase) activity that can be inhibited by the immunosuppressant FK506. The cloning and sequencing of mip genes from three different L. pneumophila strains revealed a single amino acid substitution which did not affect the isomerase property of the enzyme. Mip proteins isolated from two wild-type L. pneumophila strains and from two corresponding Escherichia coli K-12 recombinant clones derived from these strains exhibited identical enzymatic properties and the precursor proteins are processed at identical cleavage sites. The mature Mip proteins exist in an oligomeric form. Site-directed mutagenesis demonstrated that a substitution of an Asp residue at position 142 by a Leu residue affects PPIase activity of Mip.
嗜肺军团菌的Mip（“巨噬细胞感染增强因子”）蛋白已被证明是一种必需的毒力因子，具有肽基脯氨酰顺反异构酶（PPIase）活性，该活性可被免疫抑制剂FK506抑制。对来自三种不同嗜肺军团菌菌株的mip基因进行克隆和测序，发现了一个单一氨基酸取代，该取代不影响该酶的异构酶特性。从两种野生型嗜肺军团菌菌株以及从这些菌株衍生的两种相应大肠杆菌K-12重组克隆中分离出的Mip蛋白表现出相同的酶学特性，并且前体蛋白在相同的切割位点进行加工。成熟的Mip蛋白以寡聚体形式存在。定点诱变表明，将第142位的天冬氨酸残基替换为亮氨酸残基会影响Mip的PPIase活性。
