Filament formation and function of the bacterial cytoskeletal element MreB

MreB与肌动蛋白同源，在细菌中广泛保守。对于许多物种来说，MreB在细胞形状维持中起着至关重要的作用，并确保细胞壁的适当三维延伸。MreB在细胞膜下形成短丝状结构，通过两亲螺旋或MreB上的疏水贴片固定在细胞膜上。细丝相对于杆状或螺旋状细胞的长轴垂直或轻微倾斜旋转，显然是由膜整合酶的转糖基酶活性驱动的，这种酶可以延长细胞壁上的聚糖链，从而导致细胞壁生长。我们观察到MreB丝动力学和MreB成丝聚合受到生长条件的强烈影响，营养枯竭或胁迫条件导致MreB动力学强烈降低。由于MreB被证明与翻译伸长因子EF-Tu相互作用，我们计划研究这种相互作用是否将细胞营养状况的信息传递给MreB细丝，或者是否严格响应或相互作用者RodZ起作用。我们还想研究MreB是否可以直接感知细胞中的离子条件。我们计划识别和研究可能将信号传递给MreB的其他动态相互作用，我们将研究EF-Tu和RodZ对MreB丝结构的体外影响。

MreB is homologous to actin and widely conserved in bacteria. For many species, MreB plays a crucial role in cell shape maintenance, and ensures proper three-dimensional extension of the cell wall. MreB forms short filamentous structures underneath the cell membrane, which are anchored in the membrane through an amphipathic helix or a hydrophobic patch on MreB. Filaments rotate perpendicular or slightly tilted relative to the long axis of rod shaped or helical cells, apparently driven by the transglycosylase activity of membrane-integral enzymes that extend glycan strands in the cell wall, and thus lead to cell wall growth. We have observed that MreB filament dynamics and polymerization of MreB into filaments is strongly affected by growth conditions, nutrient depletion or stress conditions lead to strong reduction on MreB dynamics. Because MreB was shown to interact with translation elongation factor EF-Tu we plan to investigate if this interaction transduces information on the nutritional status of cells to MreB filaments, or if stringent response or interactor RodZ play a role. We would also like to investigate if MreB can directly sense ionic conditions in the cell. We plan to identify and study additional, dynamic interactors that might transduce signals to MreB, and we will study in vitro effects of EF-Tu and RodZ on MreB filament architecture.