5mk2
From Proteopedia
Crystal structure of the His Domain Protein Tyrosine Phosphatase (HD-PTP/PTPN23) Bro1 domain (CHMP4B peptide complex structure)
Structural highlights
Disease[CHM4B_HUMAN] Defects in CHMP4B are the cause of cataract posterior polar type 3 (CTPP3) [MIM:605387]. A subcapsular opacity, usually disk-shaped, located at the back of the lens. It can have a marked effect on visual acuity.[1] Function[PTN23_HUMAN] Plays a role in sorting of endocytic ubiquitinated cargos into multivesicular bodies (MVBs) via its interaction with the ESCRT-I complex (endosomal sorting complex required for transport I), and possibly also other ESCRT complexes. May act as a negative regulator of Ras-mediated mitogenic activity. Plays a role in ciliogenesis.[2] [3] [4] [CHM4B_HUMAN] Probable core 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. When overexpressed, membrane-assembled circular arrays of CHMP4B filaments can promote or stabilize negative curvature and outward budding. Via its interaction with PDCD6IP involved in HIV-1 p6- and p9-dependent virus release.[5] [6] [7] [8] [9] Publication Abstract from PubMedSARA and endofin are endosomal adaptor proteins that drive Smad phosphorylation by ligand-activated transforming growth factor beta/bone morphogenetic protein (TGFbeta/BMP) receptors. We show in this study that SARA and endofin also recruit the tumor supressor HD-PTP, a master regulator of endosomal sorting and ESCRT-dependent receptor downregulation. High-affinity interactions occur between the SARA/endofin N termini, and the conserved hydrophobic region in the HD-PTP Bro1 domain that binds CHMP4/ESCRT-III. CHMP4 engagement is a universal feature of Bro1 proteins, but SARA/endofin binding is specific to HD-PTP. Crystallographic structures of HD-PTPBro1 in complex with SARA, endofin, and three CHMP4 isoforms revealed that all ligands bind similarly to the conserved site but, critically, only SARA/endofin interact at a neighboring pocket unique to HD-PTP. The structures, together with mutagenesis and binding analysis, explain the high affinity and specific binding of SARA/endofin, and why they compete so effectively with CHMP4. Our data invoke models for how endocytic regulation of TGFbeta/BMP signaling is controlled. Structural Basis for Specific Interaction of TGFbeta Signaling Regulators SARA/Endofin with HD-PTP.,Gahloth D, Levy C, Walker L, Wunderley L, Mould AP, Taylor S, Woodman P, Tabernero L Structure. 2017 Jul 5;25(7):1011-1024.e4. doi: 10.1016/j.str.2017.05.005. Epub, 2017 Jun 8. PMID:28602823[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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