title: Crystal structure of truncated human apolipoprotein A-I suggests a lipid-bound conformation.
abstract: The structure of truncated human apolipoprotein A-I (apo A-I), the major protein component of high density lipoprotein, has been determined at 4-A resolution. The crystals comprise residues 44-243 (exon 4) of apo A-I, a fragment that binds to lipid similarly to intact apo A-I and that retains the lipid-bound conformation even in the absence of lipid. The molecule consists almost entirely of a pseudo-continuous, amphipathic alpha-helix that is punctuated by kinks at regularly spaced proline residues; it adopts a shape similar to a horseshoe of dimensions 125 x 80 x 40 A. Four molecules in the asymmetric unit associate via their hydrophobic faces to form an antiparallel four-helix bundle with an elliptical ring shape. Based on this structure, we propose a model for the structure of apo A-I bound to high density lipoprotein.
authors.affiliation: Department of Organic Chemistry, Southern Research Institute, Birmingham, AL 35205, USA. borhani@sri.org
authors.forename: D W
authors.initials: DW
authors.lastname: Borhani
authors.forename: D P
authors.initials: DP
authors.lastname: Rogers
authors.forename: J A
authors.initials: JA
authors.lastname: Engler
authors.forename: C G
authors.initials: CG
authors.lastname: Brouillette
mesh_terms: D000595:Amino Acid Sequence; D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D016632:Apolipoprotein A-I; D008055:Lipids