1nep
Crystal Structure Analysis of the Bovine NPC2 (Niemann-Pick C2) Protein
Structural highlights
FunctionNPC2_BOVIN Intracellular cholesterol transporter which acts in concert with NPC1 and plays an important role in the egress of cholesterol from the endosomal/lysosomal compartment. Both NPC1 and NPC2 function as the cellular 'tag team duo' (TTD) to catalyze the mobilization of cholesterol within the multivesicular environment of the late endosome (LE) to effect egress through the limiting bilayer of the LE. NPC2 binds unesterified cholesterol that has been released from LDLs in the lumen of the late endosomes/lysosomes and transfers it to the cholesterol-binding pocket of the N-terminal domain of NPC1. Cholesterol binds to NPC1 with the hydroxyl group buried in the binding pocket and is exported from the limiting membrane of late endosomes/ lysosomes to the ER and plasma membrane by an unknown mechanism. The secreted form of NCP2 regulates biliary cholesterol secretion via stimulation of ABCG5/ABCG8-mediated cholesterol transport.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedNiemann-Pick disease type C2 (NP-C2) is a fatal hereditary disease characterized by accumulation of low-density lipoprotein-derived cholesterol in lysosomes. Here we report the 1.7-A resolution crystal structure of the cholesterol-binding protein deficient in this disease, NPC2, and the characterization of its ligand binding properties. Human NPC2 binds the cholesterol analog dehydroergosterol with submicromolar affinity at both acidic and neutral pH. NPC2 has an Ig-like fold stabilized by three disulfide bonds. The structure of the bovine protein reveals a loosely packed region penetrating from the surface into the hydrophobic core that forms adjacent small cavities with a total volume of approximately 160 A(3). We propose that this region represents the incipient cholesterol-binding site that dilates to accommodate an approximately 740-A(3) cholesterol molecule. Structure of a cholesterol-binding protein deficient in Niemann-Pick type C2 disease.,Friedland N, Liou HL, Lobel P, Stock AM Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2512-7. Epub 2003 Feb 18. PMID:12591954[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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