26634441

PMC4684769

The endosomal sorting complexes required for transport (ESCRT) proteins mediate fundamental membrane remodeling events that require stabilizing negative membrane curvature. These include endosomal intralumenal vesicle formation, HIV budding, nuclear envelope closure, and cytokinetic abscission. ESCRT-III subunits perform key roles in these processes by changing conformation and polymerizing into membrane-remodeling filaments. Here, we report the 4 angstrom resolution cryogenic electron microscopy reconstruction of a one-start, double-stranded helical copolymer composed of two different human ESCRT-III subunits, charged multivesicular body protein 1B (CHMP1B) and increased sodium tolerance 1 (IST1). The inner strand comprises "open" CHMP1B subunits that interlock in an elaborate domain-swapped architecture and is encircled by an outer strand of "closed" IST1 subunits. Unlike other ESCRT-III proteins, CHMP1B and IST1 polymers form external coats on positively curved membranes in vitro and in vivo. Our analysis suggests how common ESCRT-III filament architectures could stabilize different degrees and directions of membrane curvature.

CDC Public Access

1DP2GM110772-01/DP/NCCDPHP CDC HHS/United States
1P01 GM063210/GM/NIGMS NIH HHS/United States
2P50GM082545-06/GM/NIGMS NIH HHS/United States
DP2 GM110772/GM/NIGMS NIH HHS/United States
P01 GM063210/GM/NIGMS NIH HHS/United States
P41 RR17573/RR/NCRR NIH HHS/United States
P50 GM082545/GM/NIGMS NIH HHS/United States
R01 AI051174/AI/NIAID NIH HHS/United States
R01AI051174/AI/NIAID NIH HHS/United States
R01GM076686/GM/NIGMS NIH HHS/United States
R01GM112080/GM/NIGMS NIH HHS/United States
R01NS050717/NS/NINDS NIH HHS/United States