Leaver Mark, Errington Jeff
Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK.
Mol Microbiol. 2005 Sep;57(5):1196-209. doi: 10.1111/j.1365-2958.2005.04736.x.
Actin homologues of the MreB family have an important role in specifying the morphology of many non-spherical eubacteria. The mreC and mreD genes have been implicated in control of cell morphology but their precise functions are unknown. In Bacillus subtilis the MreB homologue Mbl directs helical insertion of new cell wall material in the cylindrical part of the rod-shaped cell. Depletion of either MreC or MreD abolishes the control of cell shape. In the presence of high concentrations of magnesium cells depleted of MreC or MreD can be propagated indefinitely, although they have a spheroidal shape. We show that growth of the spheroidal mutants is based on insertion of new wall material at cell division sites and that this localized growth is dependent on cell division. Under some conditions the MreC and MreD proteins localize in a helical configuration. This localization pattern resembles that of the helical cables of Mbl protein. These results suggest that MreC and MreD act in a morphogenic pathway that couples the helical cytosolic Mbl cables to the extracellular cell wall synthetic machinery, which is critical for cylindrical elongation of the rod-shaped cells.
MreB家族的肌动蛋白同源物在决定许多非球形真细菌的形态方面发挥着重要作用。mreC和mreD基因与细胞形态控制有关，但其确切功能尚不清楚。在枯草芽孢杆菌中，MreB同源物Mbl指导新细胞壁材料在杆状细胞圆柱形部分的螺旋状插入。MreC或MreD的缺失会消除对细胞形状的控制。在高浓度镁存在的情况下，缺失MreC或MreD的细胞可以无限繁殖，尽管它们呈球形。我们表明，球形突变体的生长基于新壁材料在细胞分裂位点的插入，并且这种局部生长依赖于细胞分裂。在某些条件下，MreC和MreD蛋白呈螺旋状分布。这种定位模式类似于Mbl蛋白的螺旋状纤维束。这些结果表明，MreC和MreD在一个形态发生途径中起作用，该途径将螺旋状的胞质Mbl纤维束与细胞外细胞壁合成机制联系起来，这对杆状细胞的圆柱形伸长至关重要。
