6ze9
From Proteopedia
Non-native fold of the putative VPS39 zinc finger domain
Structural highlights
Function[VPS39_HUMAN] Regulator of TGF-beta/activin signaling, inhibiting SMAD3- and activating SMAD2-dependent transcription. Acts by interfering with SMAD3/SMAD4 complex formation, this would lead to inhibition of SMAD3-dependent transcription and relieve SMAD3 inhibition of SMAD2-dependent promoters, thus increasing SMAD2-dependent transcription. Does not affect TGF-beta-induced SMAD2 or SMAD3 phosphorylation, nor SMAD2/SMAD4 complex formation.[1] Plays a role in vesicle-mediated protein trafficking to lysosomal compartments including the endocytic membrane transport and autophagic pathways. Believed to act in part as a component of the putative HOPS endosomal tethering complex which is proposed to be involved in the Rab5-to-Rab7 endosome conversion probably implicating MON1A/B, and via binding SNAREs and SNARE complexes to mediate tethering and docking events during SNARE-mediated membrane fusion. The HOPS complex is proposed to be recruited to Rab7 on the late endosomal membrane and to regulate late endocytic, phagocytic and autophagic traffic towards lysosomes (PubMed:23351085). Involved in homotypic vesicle fusions between late endosomes and in heterotypic fusions between late endosomes and lysosomes (PubMed:11448994, PubMed:23351085, PubMed:23167963). Required for fusion of endosomes and autophagosomes with lysosomes (PubMed:25783203).[2] [3] [4] [5] Publication Abstract from PubMedBackground: The multi-subunit homotypic fusion and vacuole protein sorting (HOPS) membrane-tethering complex is involved in regulating the fusion of late endosomes and autophagosomes with lysosomes in eukaryotes. The C-terminal regions of several HOPS components have been shown to be required for correct complex assembly, including the C-terminal really interesting new gene (RING) zinc finger domains of HOPS components VPS18 and VPS41. We sought to structurally characterise the putative C-terminal zinc finger domain of VPS39, which we hypothesised may be important for binding of VPS39 to cellular partners or to other HOPS components. Methods: We recombinantly expressed, purified and solved the crystal structure of the proposed zinc-binding region of VPS39. Results: In the structure, this region forms an anti-parallel beta-hairpin that is incorporated into a homotetrameric eight-stranded beta-barrel. However, the fold is stabilised by coordination of zinc ions by residues from the purification tag and an intramolecular disulphide bond between two predicted zinc ligands. Conclusions: We solved the structure of the VPS39 C-terminal domain adopting a non-native fold. Our work highlights the risk of non-native folds when purifying small zinc-containing domains with hexahistidine tags. However, the non-native structure we observe may have implications for rational protein design. Non-native fold of the putative VPS39 zinc finger domain.,Butt BG, Scourfield EJ, Graham SC Wellcome Open Res. 2020 Jul 1;5:154. doi: 10.12688/wellcomeopenres.16078.1., eCollection 2020. PMID:32724865[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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