5h2c | pdb_00005h2c
Crystal structure of Saccharomyces cerevisiae Osh1 ANK - Nvj1
Structural highlights
Function[OSH1_YEAST] Lipid-binding protein involved in maintenance of intracellular sterol distribution and homeostasis. Binds to phosphoinositides. May be involved in formation of PMN vesicles by altering the membrane lipid composition.[1] [NVJ1_YEAST] Involved in the formation of nucleus-vacuole (NV) junctions during piecemeal microautophagy of the nucleus (PMN). NV junctions are interorganelle interfaces mediated by NVJ1 in the nuclear envelope and VAC8 on the vacuole membrane. Together, NVJ1 and VAC8 form Velcro-like patches through which teardrop-like portions of the nucleus are pinched off into the vacuolar lumen and degraded by the PMN process. Acts also as an outer-nuclear membrane receptor for OSH1 and TSC13.[2] [3] [4] [5] [6] Publication Abstract from PubMedYeast Osh1 belongs to the oxysterol-binding protein (OSBP) family of proteins and contains multiple targeting modules optimized for lipid transport at the nucleus-vacuole junction (NVJ). The key determinants for NVJ targeting and the role of Osh1 at NVJs have remained elusive because of unknown lipid specificities. In this study, we determined the structures of the ankyrin repeat domain (ANK), and OSBP-related domain (ORD) of Osh1, in complex with Nvj1 and ergosterol, respectively. The Osh1 ANK forms a unique bi-lobed structure that recognizes a cytosolic helical segment of Nvj1. We discovered that Osh1 ORD binds ergosterol and phosphatidylinositol 4-phosphate PI(4)P in a competitive manner, suggesting counter-transport function of the two lipids. Ergosterol is bound to the hydrophobic pocket in a head-down orientation, and the structure of the PI(4)P-binding site in Osh1 is well conserved. Our results suggest that Osh1 performs non-vesicular transport of ergosterol and PI(4)P at the NVJ. Structure of Yeast OSBP-Related Protein Osh1 Reveals Key Determinants for Lipid Transport and Protein Targeting at the Nucleus-Vacuole Junction.,Manik MK, Yang H, Tong J, Im YJ Structure. 2017 Apr 4;25(4):617-629.e3. doi: 10.1016/j.str.2017.02.010. Epub 2017, Mar 16. PMID:28319008[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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