Ofek I, Simpson W A, Beachey E H
J Bacteriol. 1982 Feb;149(2):426-33. doi: 10.1128/jb.149.2.426-433.1982.
The orientation of lipoteichoic acid (LTA) molecules on the surface of bacterial cells undoubtedly is determined by the ability of the LTA, during its transit through the cell wall, to bind via its polyglycerophosphate backbone or its glycolipid moieties to other constituents of the cytoplasmic membrane and the cell wall. We have investigated the possibility that LTA may become anchored to the cell surface by binding through its polyanionic backbone to positively charged regions of cell wall proteins. LTA was found to prevent the precipitation of partially purified HCl extracts of several strains of streptococci as well as a structurally defined streptococcal M protein molecule (pep M24) in 83% solutions of ethanol. The formation of complexes between LTA and M protein was demonstrated further by immunoelectrophoresis of pep M24 protein with increasing concentrations of radiolabeled LTA and by using antiserum against pep M24 to develop precipitin arcs. Pep M24 electrophoresed alone produced a single precipitin arc close to the origin. In contrast, when electrophoresed as a mixture with LTA or deacylated LTA, the M protein produced a second precipitin arc toward the anode coinciding with the area of migration of the radioactive LTA. Increasing concentrations of LTA or deacylated LTA shifted increasing amounts of the pep M24 antigen to the region of the second arc. Maleylation of M protein to block the positively charged free amino groups before mixing it with LTA prevented the formation of complexes. The complexes formed by the M protein with LTA, but not with deacylated LTA, showed the capacity to bind bovine serum albumin; LTA had been shown previously to bind to the fatty acid binding sites on bovine serum albumin. These results indicate that the LTA molecule is able to bind via its polyanionic backbone to positively charged residues of surface proteins of cells of S. pyogenes. The implications of such interaction as to the orientation of LTA molecules on the surface of cells of S. pyogenes are discussed.
脂磷壁酸（LTA）分子在细菌细胞表面的取向无疑是由LTA在穿过细胞壁的过程中，通过其聚甘油磷酸主链或糖脂部分与细胞质膜和细胞壁的其他成分结合的能力所决定的。我们研究了LTA通过其多阴离子主链与细胞壁蛋白的带正电区域结合而锚定在细胞表面的可能性。研究发现，LTA能阻止几种链球菌菌株以及一种结构明确的链球菌M蛋白分子（pep M24）的部分纯化HCl提取物在83%乙醇溶液中沉淀。通过用浓度递增的放射性标记LTA对pep M24蛋白进行免疫电泳，并使用抗pep M24抗血清产生沉淀弧，进一步证明了LTA与M蛋白之间复合物的形成。单独电泳的pep M24产生靠近原点的单一沉淀弧。相比之下，当与LTA或去酰化LTA混合电泳时，M蛋白会在阳极方向产生第二条沉淀弧，与放射性LTA的迁移区域重合。LTA或去酰化LTA浓度的增加会使越来越多的pep M24抗原转移到第二条弧的区域。在将M蛋白与LTA混合之前，对其进行马来酰化以封闭带正电的游离氨基，可防止复合物的形成。M蛋白与LTA而非去酰化LTA形成的复合物显示出结合牛血清白蛋白的能力；此前已证明LTA可与牛血清白蛋白上的脂肪酸结合位点结合。这些结果表明，LTA分子能够通过其多阴离子主链与化脓性链球菌细胞表面蛋白的带正电残基结合。讨论了这种相互作用对化脓性链球菌细胞表面LTA分子取向的影响。
