Research ArticleCELL BIOLOGY

Molecular insights into the human CLC-7/Ostm1 transporter

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Science Advances  12 Aug 2020:
Vol. 6, no. 33, eabb4747
DOI: 10.1126/sciadv.abb4747

Abstract

CLC family proteins translocate chloride ions across cell membranes to maintain the membrane potential, regulate the transepithelial Cl transport, and control the intravesicular pH among different organelles. CLC-7/Ostm1 is an electrogenic Cl/H+ antiporter that mainly resides in lysosomes and osteoclast ruffled membranes. Mutations in human CLC-7/Ostm1 lead to lysosomal storage disorders and severe osteopetrosis. Here, we present the cryo–electron microscopy (cryo-EM) structure of the human CLC-7/Ostm1 complex and reveal that the highly glycosylated Ostm1 functions like a lid positioned above CLC-7 and interacts extensively with CLC-7 within the membrane. Our complex structure reveals a functionally crucial domain interface between the amino terminus, TMD, and CBS domains of CLC-7. Structural analyses and electrophysiology studies suggest that the domain interaction interfaces affect the slow gating kinetics of CLC-7/Ostm1. Thus, our study deepens understanding of CLC-7/Ostm1 transporter and provides insights into the molecular basis of the disease-related mutations.

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