Department of Biochemistry, University of Geneva, CH-1211 Geneva, Switzerland.
Swiss National Centre for Competence in Research Programme Chemical Biology, CH-1211 Geneva, Switzerland.
Proc Natl Acad Sci U S A. 2017 May 23;114(21):5449-5454. doi: 10.1073/pnas.1619578114. Epub 2017 May 8.
Dynamin is a dimeric GTPase that assembles into a helix around the neck of endocytic buds. Upon GTP hydrolysis, dynamin breaks these necks, a reaction called membrane fission. Fission requires dynamin to first constrict the membrane. It is unclear, however, how dynamin helix constriction works. Here we undertake a direct high-speed atomic force microscopy imaging analysis to visualize the constriction of single dynamin-coated membrane tubules. We show GTP-induced dynamic rearrangements of the dynamin helix turns: the average distances between turns reduce with GTP hydrolysis. These distances vary, however, over time because helical turns were observed to transiently pair and dissociate. At fission sites, these cycles of association and dissociation were correlated with relative lateral displacement of the turns and constriction. Our findings show relative longitudinal and lateral displacements of helical turns related to constriction. Our work highlights the potential of high-speed atomic force microscopy for the observation of mechanochemical proteins onto membranes during action at almost molecular resolution.
动力蛋白是一种二聚体 GTP 酶，它会在胞吞泡的颈部组装成一个螺旋。在 GTP 水解后，动力蛋白会使这些颈部断裂，这一反应称为膜裂变。裂变需要动力蛋白首先收缩膜。然而，动力蛋白螺旋收缩的工作机制尚不清楚。在这里，我们进行了直接的高速原子力显微镜成像分析，以可视化单个动力蛋白包被的膜小管的收缩。我们展示了 GTP 诱导的动力蛋白螺旋构象的动态重排：随着 GTP 水解，螺旋各圈之间的平均距离减小。然而，这些距离随时间变化，因为观察到螺旋圈会暂时配对和解离。在裂变部位，这些关联和解离的循环与螺旋圈的相对侧向位移和收缩相关。我们的发现表明，螺旋圈的相对纵向和侧向位移与收缩有关。我们的工作强调了高速原子力显微镜在观察作用于膜的机械化学蛋白方面的潜力，其分辨率几乎达到了分子水平。
