Download MendeleyStructural Basis of Sterol Binding by NPC2, a Lysosomal Protein Deficient in Niemann-Pick Type C2 Disease
Xu, S., Benoff, B., Liou, H.-L., Lobel, P., Stock, A.M.(2007) J Biol Chem 282: 23525-23531
- PubMed: 17573352
- DOI: https://doi.org/10.1074/jbc.M703848200
- Primary Citation of Related Structures:
2HKA - PubMed 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 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.
Organizational Affiliation:
Center for Advanced Biotechnology and Medicine, Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
