4txr
From Proteopedia
Crystal structure of LIP5 N-terminal domain complexed with CHMP1B MIM and CHMP5 MIM
Structural highlights
FunctionCHM1B_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 cytokinesis. Involved in recruiting VPS4A and/or VPS4B and SPAST to the midbody of dividing cells. Involved in HIV-1 p6- and p9-dependent virus release.[1] [2] Publication Abstract from PubMedDisassembly of the endosomal sorting complex required for transport (ESCRT) machinery from biological membranes is a critical final step in cellular processes that require the ESCRT function. This reaction is catalyzed by VPS4, a AAA-ATPase whose activity is tightly regulated by a host of proteins including LIP5 and the ESCRT-III proteins. Here, we present structural and functional analyses of molecular interactions between human VPS4, LIP5 and the ESCRT-III proteins. The N-terminal domain of LIP5 (LIP5NTD) is required for LIP5-mediated stimulation of VPS4 and the ESCRT-III protein CHMP5 strongly inhibits the stimulation. Both of these observations are distinct from what was previously described for homologous yeast proteins. The crystal structure of LIP5NTD in complex with the MIT-interacting motifs (MIMs) of CHMP5 and a second ESCRT-III protein CHMP1B was determined at 1 angstrom resolution. It reveals an ESCRT-III binding induced moderate conformational change in LIP5NTD, which results from insertion of a conserved CHMP5 tyrosine residue (Tyr182) at the core of LIP5NTD structure. Mutation of Tyr182 partially relieves the inhibition displayed by CHMP5. Together, these results suggest a novel mechanism of VPS4 regulation in metazoans, where CHMP5 functions as a negative allosteric switch to control LIP5-mediated stimulation of VPS4. A Novel Mechanism of Regulating the ATPase VPS4 by Its Cofactor LIP5 and the Endosomal Sorting Complex Required for Transport (ESCRT)-III Protein CHMP5.,Vild CJ, Li Y, Guo EZ, Liu Y, Xu Z J Biol Chem. 2015 Jan 30. pii: jbc.M114.616730. PMID:25637630[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also
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