Eckstein Torsten M, Belisle John T, Inamine Julia M
Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523-1682, USA.
Microbiology (Reading). 2003 Oct;149(Pt 10):2797-2807. doi: 10.1099/mic.0.26528-0.
Members of the Mycobacterium avium complex are distinguished by the presence of highly antigenic surface molecules called glycopeptidolipids (GPLs) and the oligosaccharide portion of the serovar-specific GPL defines the 28 serovars. Previously, the genomic region (ser2) encoding the enzymes responsible for the glycosylation of the lipopeptide core to generate the serovar-2-specific GPLs has been described. In this work, the ser2 gene clusters of M. avium serovar 2 strains 2151 and TMC 724 were fully sequenced and compared to the homologous regions of M. avium serovar 1 strain 104, M. avium subsp. paratuberculosis and M. avium subsp. silvaticum. It was also determined that 104Rg, a mutant of strain 104 that produces truncated GPLs, lost several GPL biosynthesis genes by deletion. This comparison, together with analysis of protein similarities, supports a biosynthetic model in which serovar-2-specific GPLs are synthesized from a serovar-1-specific GPL intermediate that is derived from a non-specific GPL precursor. We also identified a gene encoding an enzyme that is necessary for the biosynthesis of serovar-3- and 9-specific GPLs, but not serovar-2-specific GPLs, suggesting that the different serovars may have evolved from the acquisition or loss of genetic information. In addition, a subcluster of genes for the biosynthesis and transfer of fucose, which are needed to make serovar-specific GPLs such as those of serovar 2, is found in the non-GPL-producing M. avium subspecies paratuberculosis and silvaticum.
鸟分枝杆菌复合群的成员通过存在称为糖肽脂（GPLs）的高度抗原性表面分子来区分，血清型特异性GPL的寡糖部分定义了28个血清型。此前，已经描述了编码负责脂肽核心糖基化以产生血清型2特异性GPLs的酶的基因组区域（ser2）。在这项工作中，对鸟分枝杆菌血清型2菌株2151和TMC 724的ser2基因簇进行了全序列测定，并与鸟分枝杆菌血清型1菌株104、副结核分枝杆菌亚种和鸟分枝杆菌亚种的同源区域进行了比较。还确定了产生截短GPLs的菌株104的突变体104Rg通过缺失失去了几个GPL生物合成基因。这种比较以及蛋白质相似性分析支持了一种生物合成模型，即血清型2特异性GPLs由源自非特异性GPL前体的血清型1特异性GPL中间体合成。我们还鉴定了一个编码一种酶的基因，该酶是血清型3和9特异性GPLs生物合成所必需的，但不是血清型2特异性GPLs生物合成所必需的，这表明不同的血清型可能是通过遗传信息的获得或丧失而进化的。此外，在不产生GPL的副结核分枝杆菌亚种和鸟分枝杆菌亚种中发现了一组用于岩藻糖生物合成和转移的基因亚簇，岩藻糖是制造血清型特异性GPLs（如血清型2的GPLs）所必需的。
