Kaur Devinder, McNeil Michael R, Khoo Kay-Hooi, Chatterjee Delphi, Crick Dean C, Jackson Mary, Brennan Patrick J
Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, 80523, the.
Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan, and the.
J Biol Chem. 2007 Sep 14;282(37):27133-27140. doi: 10.1074/jbc.M703389200. Epub 2007 Jul 2.
Genetic construction of a mutant strain (designated MSMEG4245) of Mycobacterium smegmatis, defective in a broadly conserved gene for a putative glycosyltransferase of the glycosyltransferase-C superfamily, results in a phenotype marked by the virtual absence of the phosphatidylinositol-containing lipomannan and lipoarabinomannan, replaced instead by a novel truncated form of lipomannan. The normal spectrum of phosphatidylinositol mannosides, long presumed precursors of these lipoglycans, was retained. Matrix-assisted laser desorption/ionization-time of flight/mass spectrometry of the mutated form of lipomannan shows a family of phosphatidylinositol-anchored lipomannans with from only 5 to 20 Manp residues as compared with lipomannan from the wild type strain consisting of 21-34 Manp residues but with few changes in the branching pattern. Thus, MSMEG4245 is apparently a key mannosyltransferase, required for the proper elongation of lipomannan to its normal state and subsequent synthesis of lipoarabinomannan. The corresponding ortholog in Mycobacterium tuberculosis H37Rv has been identified as Rv2174. This previously unrecognized feature of the biosynthesis of lipomannan/lipoarabinomannan allows a significant revision of structural and biosynthetic schemata and provides a molecular basis of selectivity in biosynthesis, as conferred by the MSMEG4245 gene.
耻垢分枝杆菌突变株(命名为MSMEG4245)的基因构建,该突变株在糖基转移酶 - C超家族中一个广泛保守的假定糖基转移酶基因上存在缺陷,导致一种表型,其特征是几乎不存在含磷脂酰肌醇的脂甘露聚糖和脂阿拉伯甘露聚糖,取而代之的是一种新型的截短形式的脂甘露聚糖。这些脂聚糖的长期假定前体——磷脂酰肌醇甘露糖苷的正常谱得以保留。突变形式的脂甘露聚糖的基质辅助激光解吸/电离飞行时间质谱显示,与野生型菌株由21 - 34个甘露糖残基组成的脂甘露聚糖相比,有一族磷脂酰肌醇锚定的脂甘露聚糖,其甘露糖残基仅为5至20个,但分支模式变化不大。因此,MSMEG4245显然是一种关键的甘露糖基转移酶,是脂甘露聚糖正常延长至其正常状态以及随后合成脂阿拉伯甘露聚糖所必需的。结核分枝杆菌H37Rv中的相应直系同源基因已被鉴定为Rv2174。脂甘露聚糖/脂阿拉伯甘露聚糖生物合成的这一先前未被认识的特征允许对结构和生物合成模式进行重大修订,并提供了由MSMEG4245基因赋予的生物合成选择性的分子基础。