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Title: Structural Basis of Sterol Binding by NPC2, a Lysosomal Protein Deficient in Niemann-Pick Type C2 Disease

Abstract

NPC2 is a small lysosomal glycoprotein that binds cholesterol with submicromolar affinity. Deficiency in NPC2 is the cause of Niemann-Pick type C2 disease, a fatal neurovisceral disorder characterized by accumulation of cholesterol in lysosomes. Here we report the crystal structure of bovine NPC2 bound to cholesterol-3-O-sulfate, an analog that binds with greater apparent affinity than cholesterol. Structures of both apo-bound and sterol-bound NPC2 were observed within the same crystal lattice, with an asymmetric unit containing one molecule of apoNPC2 and two molecules of sterol-bound NPC2. As predicted from a previously determined structure of apoNPC2, the sterol binds in a deep hydrophobic pocket sandwiched between the two {beta}-sheets of NPC2, with only the sulfate substituent of the ligand exposed to solvent. In the two available structures of apoNPC2, the incipient ligand-binding pocket, which ranges from a loosely packed hydrophobic core to a small tunnel, is too small to accommodate cholesterol. In the presence of sterol, the pocket expands, facilitated by a slight separation of the {beta}-strands and substantial reorientation of some side chains, resulting in a perfect molding of the pocket around the hydrocarbon portion of cholesterol. A notable feature is the repositioning of two aromatic residues at the tunnel entrancemore » that are essential for NPC2 function. The NPC2 structures provide evidence of a malleable binding site, consistent with the previously documented broad range of sterol ligand specificity.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929992
Report Number(s):
BNL-80601-2008-JA
Journal ID: ISSN 0021-9258; JBCHA3; TRN: US200822%%1147
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Biological Chemistry; Journal Volume: 282; Journal Issue: 32
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AFFINITY; AROMATICS; BUILDUP; CATTLE; CHOLESTEROL; CRYSTAL LATTICES; CRYSTAL STRUCTURE; DISEASES; GLYCOPROTEINS; HYDROCARBONS; LIGANDS; LYSOSOMES; MOLDING; MOLECULES; PROTEINS; RANGE; RESIDUES; SPECIFICITY; STEROLS; SULFATES; TUNNELS; UNITS; national synchrotron light source

Citation Formats

Xu,S., Benoff, B., Liou, H., Lobel, P., and Stock, A.. Structural Basis of Sterol Binding by NPC2, a Lysosomal Protein Deficient in Niemann-Pick Type C2 Disease. United States: N. p., 2007. Web. doi:10.1074/jbc.M703848200.
Xu,S., Benoff, B., Liou, H., Lobel, P., & Stock, A.. Structural Basis of Sterol Binding by NPC2, a Lysosomal Protein Deficient in Niemann-Pick Type C2 Disease. United States. doi:10.1074/jbc.M703848200.
Xu,S., Benoff, B., Liou, H., Lobel, P., and Stock, A.. Mon . "Structural Basis of Sterol Binding by NPC2, a Lysosomal Protein Deficient in Niemann-Pick Type C2 Disease". United States. doi:10.1074/jbc.M703848200.
@article{osti_929992,
title = {Structural Basis of Sterol Binding by NPC2, a Lysosomal Protein Deficient in Niemann-Pick Type C2 Disease},
author = {Xu,S. and Benoff, B. and Liou, H. and Lobel, P. and Stock, A.},
abstractNote = {NPC2 is a small lysosomal glycoprotein that binds cholesterol with submicromolar affinity. Deficiency in NPC2 is the cause of Niemann-Pick type C2 disease, a fatal neurovisceral disorder characterized by accumulation of cholesterol in lysosomes. Here we report the crystal structure of bovine NPC2 bound to cholesterol-3-O-sulfate, an analog that binds with greater apparent affinity than cholesterol. Structures of both apo-bound and sterol-bound NPC2 were observed within the same crystal lattice, with an asymmetric unit containing one molecule of apoNPC2 and two molecules of sterol-bound NPC2. As predicted from a previously determined structure of apoNPC2, the sterol binds in a deep hydrophobic pocket sandwiched between the two {beta}-sheets of NPC2, with only the sulfate substituent of the ligand exposed to solvent. In the two available structures of apoNPC2, the incipient ligand-binding pocket, which ranges from a loosely packed hydrophobic core to a small tunnel, is too small to accommodate cholesterol. In the presence of sterol, the pocket expands, facilitated by a slight separation of the {beta}-strands and substantial reorientation of some side chains, resulting in a perfect molding of the pocket around the hydrocarbon portion of cholesterol. A notable feature is the repositioning of two aromatic residues at the tunnel entrance that are essential for NPC2 function. The NPC2 structures provide evidence of a malleable binding site, consistent with the previously documented broad range of sterol ligand specificity.},
doi = {10.1074/jbc.M703848200},
journal = {Journal of Biological Chemistry},
number = 32,
volume = 282,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}