3um1
Crystal structure of the Brox Bro1 domain in complex with the C-terminal tail of CHMP5
Structural highlights
FunctionCHMP5_HUMAN Probable peripherally associated component of the endosomal sorting required for transport complex III (ESCRT-III) which is involved in multivesicular bodies (MVBs) formation and sorting of endosomal cargo proteins into MVBs. MVBs contain intraluminal vesicles (ILVs) that are generated by invagination and scission from the limiting membrane of the endosome and mostly are delivered to lysosomes enabling degradation of membrane proteins, such as stimulated growth factor receptors, lysosomal enzymes and lipids. The MVB pathway appears to require the sequential function of ESCRT-O, -I,-II and -III complexes. ESCRT-III proteins mostly dissociate from the invaginating membrane before the ILV is released. The ESCRT machinery also functions in topologically equivalent membrane fission events, such as the terminal stages of cytokinesis and the budding of enveloped viruses (HIV-1 and other lentiviruses). ESCRT-III proteins are believed to mediate the necessary vesicle extrusion and/or membrane fission activities, possibly in conjunction with the AAA ATPase VPS4. Involved in HIV-1 p6- and p9-dependent virus release.[1] Publication Abstract from PubMedInteractions of the CHMP protein carboxyl terminal tails with effector proteins play important roles in retroviral budding, cytokinesis, and multivesicular body biogenesis. Here we demonstrate that hydrophobic residues at the CHMP4B C-terminal amphipathic alpha helix bind a concave surface of Brox, a mammalian paralog of Alix. Unexpectedly, CHMP5 was also found to bind Brox and specifically recruit endogenous Brox to detergent-resistant membrane fractions through its C-terminal 20 residues. Instead of an alpha helix, the CHMP5 C-terminal tail adopts a tandem beta-hairpin structure that binds Brox at the same site as CHMP4B. Additional Brox:CHMP5 interface is furnished by a unique CHMP5 hydrophobic pocket engaging the Brox residue Y348 that is not conserved among the Bro1 domains. Our studies thus unveil a beta-hairpin conformation of the CHMP5 protein C-terminal tail, and provide insights into the overlapping but distinct binding profiles of ESCRT-III and the Bro1 domain proteins. Two Distinct Binding Modes Define the Interaction of Brox with the C-Terminal Tails of CHMP5 and CHMP4B.,Mu R, Dussupt V, Jiang J, Sette P, Rudd V, Chuenchor W, Bello NF, Bouamr F, Xiao TS Structure. 2012 May 9;20(5):887-98. Epub 2012 Apr 5. PMID:22484091[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also
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