Uenoyama Atsuko, Kusumoto Akiko, Miyata Makoto
Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585. PRESTO, JST, Osaka, Japan.
J Bacteriol. 2004 Mar;186(5):1537-45. doi: 10.1128/JB.186.5.1537-1545.2004.
Several mycoplasma species are known to glide in the direction of the membrane protrusion (head-like structure), but the mechanism underlying this movement is entirely unknown. To identify proteins involved in the gliding mechanism, protein fractions of Mycoplasma mobile were analyzed for 10 gliding mutants isolated previously. One large protein (Gli349) was observed to be missing in a mutant m13 deficient in hemadsorption and glass binding. The predicted amino acid sequence indicated a 348,758-Da protein that was truncated at amino acid residue 1257 in the mutant. Immunofluorescence microscopy with a monoclonal antibody showed that Gli349 is localized at the head-like protrusion's base, which we designated the cell neck, and immunoelectron microscopy established that the Gli349 molecules are distributed all around this neck. The number of Gli349 molecules on a cell was estimated by immunoblot analysis to be 450 +/- 200. The antibody inhibited both the hemadsorption and glass binding of M. mobile. When the antibody was used to treat gliding mycoplasmas, the gliding speed and the extent of glass binding were inhibited to similar extents depending on the concentration of the antibody. This suggested that the Gli349 molecule is involved not only in glass binding for gliding but also in movement. To explain the present results, a model for the mechanical cycle of gliding is discussed.
已知几种支原体能够朝着膜突出物（头部样结构）的方向滑行，但其背后的机制完全未知。为了鉴定参与滑行机制的蛋白质，对先前分离出的10个滑行突变体的运动支原体蛋白组分进行了分析。在一个缺乏血细胞吸附和玻璃结合能力的突变体m13中，观察到一种大蛋白（Gli349）缺失。预测的氨基酸序列表明该蛋白分子量为348,758道尔顿，在突变体中于氨基酸残基1257处被截断。用单克隆抗体进行免疫荧光显微镜观察显示，Gli349定位于头部样突出物的基部，我们将其命名为细胞颈部，免疫电子显微镜证实Gli349分子分布在这个颈部周围。通过免疫印迹分析估计，一个细胞上Gli349分子的数量为450±200。该抗体抑制了运动支原体的血细胞吸附和玻璃结合。当用该抗体处理滑行支原体时，根据抗体浓度，滑行速度和玻璃结合程度受到相似程度的抑制。这表明Gli349分子不仅参与滑行的玻璃结合，还参与运动。为了解释目前的结果，讨论了一个滑行机械循环的模型。
