Gallop Jennifer L, Jao Christine C, Kent Helen M, Butler P Jonathan G, Evans Philip R, Langen Ralf, McMahon Harvey T
MRC Laboratory of Molecular Biology, Cambridge, UK.
EMBO J. 2006 Jun 21;25(12):2898-910. doi: 10.1038/sj.emboj.7601174. Epub 2006 Jun 8.
Endophilin-A1 is a BAR domain-containing protein enriched at synapses and is implicated in synaptic vesicle endocytosis. It binds to dynamin and synaptojanin via a C-terminal SH3 domain. We examine the mechanism by which the BAR domain and an N-terminal amphipathic helix, which folds upon membrane binding, work as a functional unit (the N-BAR domain) to promote dimerisation and membrane curvature generation. By electron paramagnetic resonance spectroscopy, we show that this amphipathic helix is peripherally bound in the plane of the membrane, with the midpoint of insertion aligned with the phosphate level of headgroups. This places the helix in an optimal position to effect membrane curvature generation. We solved the crystal structure of rat endophilin-A1 BAR domain and examined a distinctive insert protruding from the membrane interaction face. This insert is predicted to form an additional amphipathic helix and is important for curvature generation. Its presence defines an endophilin/nadrin subclass of BAR domains. We propose that N-BAR domains function as low-affinity dimers regulating binding partner recruitment to areas of high membrane curvature.
内吞蛋白-A1是一种富含于突触的含BAR结构域的蛋白质，与突触小泡内吞作用有关。它通过C端的SH3结构域与发动蛋白和突触素结合。我们研究了BAR结构域和N端两亲性螺旋（在与膜结合时折叠）作为一个功能单元（N-BAR结构域）促进二聚化和膜曲率产生的机制。通过电子顺磁共振光谱，我们表明这种两亲性螺旋在膜平面上是外周结合的，插入的中点与头部基团的磷酸水平对齐。这使螺旋处于产生膜曲率的最佳位置。我们解析了大鼠内吞蛋白-A1 BAR结构域的晶体结构，并研究了从膜相互作用面突出的一个独特插入片段。该插入片段预计会形成另一个两亲性螺旋，对曲率产生很重要。它的存在定义了BAR结构域的内吞蛋白/纳德里蛋白亚类。我们提出N-BAR结构域作为低亲和力二聚体发挥作用，调节结合伴侣募集到高膜曲率区域。
