Shen Qing-Tao, Schuh Amber L, Zheng Yuqing, Quinney Kyle, Wang Lei, Hanna Michael, Mitchell Julie C, Otegui Marisa S, Ahlquist Paul, Cui Qiang, Audhya Anjon
Department of Biomolecular Chemistry, School of Medicine and Public Health, Department of Botany, Department of Genetics, Department of Chemistry, Graduate Program in Biophysics, Department of Mathematics, Department of Biochemistry, Institute for Molecular Virology, Howard Hughes Medical Institute, and Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706 Department of Biomolecular Chemistry, School of Medicine and Public Health, Department of Botany, Department of Genetics, Department of Chemistry, Graduate Program in Biophysics, Department of Mathematics, Department of Biochemistry, Institute for Molecular Virology, Howard Hughes Medical Institute, and Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706 Department of Biomolecular Chemistry, School of Medicine and Public Health, Department of Botany, Department of Genetics, Department of Chemistry, Graduate Program in Biophysics, Department of Mathematics, Department of Biochemistry, Institute for Molecular Virology, Howard Hughes Medical Institute, and Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706.
Department of Biomolecular Chemistry, School of Medicine and Public Health, Department of Botany, Department of Genetics, Department of Chemistry, Graduate Program in Biophysics, Department of Mathematics, Department of Biochemistry, Institute for Molecular Virology, Howard Hughes Medical Institute, and Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706.
J Cell Biol. 2014 Sep 15;206(6):763-77. doi: 10.1083/jcb.201403108. Epub 2014 Sep 8.
The scission of biological membranes is facilitated by a variety of protein complexes that bind and manipulate lipid bilayers. ESCRT-III (endosomal sorting complex required for transport III) filaments mediate membrane scission during the ostensibly disparate processes of multivesicular endosome biogenesis, cytokinesis, and retroviral budding. However, mechanisms by which ESCRT-III subunits assemble into a polymer remain unknown. Using cryogenic electron microscopy (cryo-EM), we found that the full-length ESCRT-III subunit Vps32/CHMP4B spontaneously forms single-stranded spiral filaments. The resolution afforded by two-dimensional cryo-EM combined with molecular dynamics simulations revealed that individual Vps32/CHMP4B monomers within a filament are flexible and able to accommodate a range of bending angles. In contrast, the interface between monomers is stable and refractory to changes in conformation. We additionally found that the carboxyl terminus of Vps32/CHMP4B plays a key role in restricting the lateral association of filaments. Our findings highlight new mechanisms by which ESCRT-III filaments assemble to generate a unique polymer capable of membrane remodeling in multiple cellular contexts.
多种结合并操控脂质双层的蛋白质复合物促进了生物膜的分裂。转运所需内体分选复合物III（ESCRT-III）细丝在多泡内体生物发生、胞质分裂和逆转录病毒出芽等表面上截然不同的过程中介导膜分裂。然而，ESCRT-III亚基组装成聚合物的机制仍然未知。利用低温电子显微镜（cryo-EM），我们发现全长ESCRT-III亚基Vps32/CHMP4B自发形成单链螺旋细丝。二维低温电子显微镜与分子动力学模拟相结合所提供的分辨率显示，细丝内的单个Vps32/CHMP4B单体具有灵活性，能够适应一系列弯曲角度。相比之下，单体之间的界面是稳定的，且构象不易改变。我们还发现，Vps32/CHMP4B的羧基末端在限制细丝的横向缔合中起关键作用。我们的研究结果突出了ESCRT-III细丝组装以生成一种能够在多种细胞环境中进行膜重塑的独特聚合物的新机制。
