Structural basis for activation, assembly and membrane binding of ESCRT-III Snf7 filaments
Shaogeng Tang,
W Mike Henne,
Peter P Borbat,
Nicholas J Buchkovich,
Jack H Freed,
Yuxin Mao,
J Christopher Fromme,
Scott D Emr
Affiliations
Shaogeng Tang
Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
W Mike Henne
Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
Peter P Borbat
National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, United States; Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
Nicholas J Buchkovich
Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
Jack H Freed
National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, United States; Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
Yuxin Mao
Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
J Christopher Fromme
Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
Scott D Emr
Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
The endosomal sorting complexes required for transport (ESCRTs) constitute hetero-oligomeric machines that catalyze multiple topologically similar membrane-remodeling processes. Although ESCRT-III subunits polymerize into spirals, how individual ESCRT-III subunits are activated and assembled together into a membrane-deforming filament remains unknown. Here, we determine X-ray crystal structures of the most abundant ESCRT-III subunit Snf7 in its active conformation. Using pulsed dipolar electron spin resonance spectroscopy (PDS), we show that Snf7 activation requires a prominent conformational rearrangement to expose protein-membrane and protein-protein interfaces. This promotes the assembly of Snf7 arrays with ~30 Å periodicity into a membrane-sculpting filament. Using a combination of biochemical and genetic approaches, both in vitro and in vivo, we demonstrate that mutations on these protein interfaces halt Snf7 assembly and block ESCRT function. The architecture of the activated and membrane-bound Snf7 polymer provides crucial insights into the spatially unique ESCRT-III-mediated membrane remodeling.
