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首页> 外文期刊>Infection and immunity >Molecular characterization of a 6.6-kilodalton Borrelia burgdorferi outer membrane-associated lipoprotein (lp6.6) which appears to be downregulated during mammalian infection.
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Molecular characterization of a 6.6-kilodalton Borrelia burgdorferi outer membrane-associated lipoprotein (lp6.6) which appears to be downregulated during mammalian infection.

机译：6.6公斤级伯氏疏螺旋体伯膜外膜相关脂蛋白（lp6.6）的分子表征，在哺乳动物感染过程中似乎被下调。

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摘要

Isolated outer membranes of Borrelia burgdorferi 297 were utilized to obtain partial amino acid sequence information for a low-molecular-weight, outer membrane-associated polypeptide. Degenerate oligonucleotide primers based upon this information were used to amplify a 100-bp probe for detection of the corresponding full-length gene within a B. burgdorferi total genomic library. The relevant open reading frame (ORF) encoded a polypeptide comprised of a 17-amino-acid putative signal peptide terminated by LFVAC, a probable consensus sequence for lipoprotein modification, and a mature protein of 51 amino acids (predicted molecular mass of 5.8 kDa). The DNA sequences of the corresponding ORFs in B. burgdorferi 297 and B31 were identical; the corresponding ORF in strain N40 differed by only one nucleotide. Assuming conventional processing and acylation, the molecular weight of the lipoprotein, designated lp6.6, is about 6,600. The lp6.6 gene, which was localized to the 49-kb linear plasmid of B. burgdorferi, subsequently was cloned and expressed in Escherichia coli as a fusion protein with glutathione S-transferase. Immunoblot analysis with monoclonal antibody 240.7 revealed that lp6.6 was identical to a low-molecular-weight, highly conserved B. burgdorferi lipoprotein reported previously (L. I. Katona, G. Beck, and G. S. Habicht, Infect. Immun. 60:4995-5003, 1992). Results of indirect immunofluorescence assays, growth inhibition assays, passive immunizations, and active immunizations indicated that this outer membrane-associated antigen is not surface exposed in B. burgdorferi. Particularly interesting was the finding that mice and rhesus monkeys chronically infected with B. burgdorferi failed to develop antibodies against this antigen. We propose that high-level expression of lp6.6 is associated with the arthropod phase of the spirochetal life cycle and that expression of the gene is downregulated during mammalian infection.
机译：利用伯氏疏螺旋体297的分离的外膜获得低分子量，外膜相关多肽的部分氨基酸序列信息。基于此信息的简并寡核苷酸引物用于扩增100 bp探针，以检测伯氏疏螺旋体总基因组文库中的相应全长基因。相关的开放阅读框（ORF）编码的多肽由LFVAC终止的17个氨基酸推定信号肽，可能的脂蛋白修饰共有序列和51个氨基酸的成熟蛋白组成（预测分子量为5.8 kDa） 。 B. burgdorferi 297和B31中相应的ORF的DNA序列相同;菌株N40中相应的ORF仅相差一个核苷酸。假定常规加工和酰化作用，脂蛋白的分子量称为lp6.6，约为6,600。定位于伯氏疏螺旋体49-kb线性质粒的lp6.6基因随后被克隆并在大肠杆菌中作为与谷胱甘肽S-转移酶的融合蛋白表达。用单克隆抗体240.7进行的免疫印迹分析表明，lp6.6与先前报道的低分子量，高度保守的伯氏疏螺旋体脂蛋白相同（LI Katona，G。Beck和GS Habicht，Infect。Immun。60：4995-5003 （1992年）。间接免疫荧光测定，生长抑制测定，被动免疫和主动免疫的结果表明，这种与外膜相关的抗原未在伯氏疏螺旋体中暴露。特别有趣的发现是，长期感染伯氏疏螺旋体的小鼠和恒河猴未能产生针对该抗原的抗体。我们建议lp6.6的高水平表达与螺旋体生命周期的节肢动物阶段有关，并且该基因的表达在哺乳动物感染期间被下调。

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