van den Ent Fusinita, Izoré Thierry, Bharat Tanmay Am, Johnson Christopher M, Löwe Jan
Structural Studies Division, Medical Research Council - Laboratory of Molecular Biology, Cambridge, United Kingdom
Structural Studies Division, Medical Research Council - Laboratory of Molecular Biology, Cambridge, United Kingdom.
Elife. 2014 May 2;3:e02634. doi: 10.7554/eLife.02634.
Filaments of all actin-like proteins known to date are assembled from pairs of protofilaments that are arranged in a parallel fashion, generating polarity. In this study, we show that the prokaryotic actin homologue MreB forms pairs of protofilaments that adopt an antiparallel arrangement in vitro and in vivo. We provide an atomic view of antiparallel protofilaments of Caulobacter MreB as apparent from crystal structures. We show that a protofilament doublet is essential for MreB's function in cell shape maintenance and demonstrate by in vivo site-specific cross-linking the antiparallel orientation of MreB protofilaments in E. coli. 3D cryo-EM shows that pairs of protofilaments of Caulobacter MreB tightly bind to membranes. Crystal structures of different nucleotide and polymerisation states of Caulobacter MreB reveal conserved conformational changes accompanying antiparallel filament formation. Finally, the antimicrobial agents A22/MP265 are shown to bind close to the bound nucleotide of MreB, presumably preventing nucleotide hydrolysis and destabilising double protofilaments.DOI: http://dx.doi.org/10.7554/eLife.02634.001.
迄今为止已知的所有肌动蛋白样蛋白的丝都是由成对的原丝组装而成，这些原丝以平行方式排列，产生极性。在本研究中，我们表明原核肌动蛋白同源物MreB形成的原丝对在体外和体内均采用反平行排列。我们从晶体结构中提供了柄杆菌属MreB反平行原丝的原子视图。我们表明原丝双联体对于MreB在维持细胞形状中的功能至关重要，并通过体内位点特异性交联证明了大肠杆菌中MreB原丝的反平行取向。三维冷冻电镜显示柄杆菌属MreB的原丝对紧密结合于膜。柄杆菌属MreB不同核苷酸和聚合状态的晶体结构揭示了伴随反平行丝形成的保守构象变化。最后，显示抗菌剂A22/MP265结合于靠近MreB结合核苷酸的位置，推测可防止核苷酸水解并使双原丝不稳定。DOI: http://dx.doi.org/10.7554/eLife.02634.001 。
