title: Clues to the mechanism of cholesterol transfer from the structure of NPC1 middle lumenal domain bound to NPC2.
abstract: Export of LDL-derived cholesterol from lysosomes requires the cooperation of the integral membrane protein Niemann-Pick C1 (NPC1) and a soluble protein, Niemann-Pick C2 (NPC2). Mutations in the genes encoding these proteins lead to Niemann-Pick disease type C (NPC). NPC2 binds to NPC1's second (middle), lumenally oriented domain (MLD) and transfers cholesterol to NPC1's N-terminal domain (NTD). Here, we report the 2.4-Å resolution crystal structure of a complex of human NPC1-MLD and NPC2 bearing bound cholesterol-3-O-sulfate. NPC1-MLD uses two protruding loops to bind NPC2, analogous to its interaction with the primed Ebola virus glycoprotein. Docking of the NPC1-NPC2 complex onto the full-length NPC1 structure reveals a direct cholesterol transfer tunnel between NPC2 and NTD cholesterol binding pockets, supporting the "hydrophobic hand-off" cholesterol transfer model.
authors.affiliation: Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065; xli05@rockefeller.edu blobel@rockefeller.edu pfeffer@stanford.edu.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305.
authors.forename: Piyali
authors.initials: P
authors.lastname: Saha
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.affiliation: Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065; xli05@rockefeller.edu blobel@rockefeller.edu pfeffer@stanford.edu.
authors.forename: Günter
authors.initials: G
authors.lastname: Blobel
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305 xli05@rockefeller.edu blobel@rockefeller.edu pfeffer@stanford.edu.
authors.forename: Suzanne R
authors.initials: SR
authors.lastname: Pfeffer
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002788:Cholesterol Esters / Q000737:chemistry* / Q000378:metabolism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005822:Genetic Vectors / Q000737:chemistry / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008247:Lysosomes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D062105:Molecular Docking Simulation; D000077296:Niemann-Pick C1 Protein; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D054730:Protein Interaction Domains and Motifs; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D002788:Cholesterol Esters; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; C106881:NPC1 protein, human; C104585:NPC2 protein, human; D000077296:Niemann-Pick C1 Protein; D011994:Recombinant Proteins; D033921:Vesicular Transport Proteins; C007045:cholesteryl sulfate
keywords: Ebola virus glycoprotein; Niemann–Pick type C disease; cholesterol trafficking; crystal structure