Isas J Mario, Ambroso Mark R, Hegde Prabhavati B, Langen Jennifer, Langen Ralf
Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA.
Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2910, USA.
Structure. 2015 May 5;23(5):873-881. doi: 10.1016/j.str.2015.02.014. Epub 2015 Apr 9.
BAR proteins are involved in a variety of membrane remodeling events but how they can mold membranes into different shapes remains poorly understood. Using electron paramagnetic resonance, we find that vesicle binding of the N-BAR protein amphiphysin is predominantly mediated by the shallow insertion of amphipathic N-terminal helices. In contrast, the interaction with tubes involves deeply inserted N-terminal helices together with the concave surface of the BAR domain, which acts as a scaffold. Combined with the observed concentration dependence of tubulation and BAR domain scaffolding, the data indicate that initial membrane deformations and vesicle binding are mediated by insertion of amphipathic helical wedges, while tubulation requires high protein densities at which oligomeric BAR domain scaffolds form. In addition, we identify a pocket of residues on the concave surface of the BAR domain that insert deeply into tube membrane. Interestingly, this pocket harbors a number of disease mutants in the homologous amphiphysin 2.
BAR蛋白参与多种膜重塑事件，但它们如何将膜塑造成不同形状仍知之甚少。利用电子顺磁共振，我们发现N-BAR蛋白发动蛋白的囊泡结合主要由两亲性N端螺旋的浅插入介导。相比之下，与管状结构的相互作用涉及深度插入的N端螺旋以及作为支架的BAR结构域的凹面。结合观察到的微管形成和BAR结构域支架的浓度依赖性，数据表明初始膜变形和囊泡结合是由两亲性螺旋楔的插入介导的，而微管形成需要高蛋白密度，此时寡聚BAR结构域支架形成。此外，我们在BAR结构域的凹面上鉴定出一个残基口袋，该口袋深深插入管状膜中。有趣的是，这个口袋包含同源发动蛋白2中的许多疾病突变体。
