The conformation of lipid-free human apolipoprotein A-I in solution. Biochemistry 2013 Dec 31;52(52):9470-81
Date
12/07/2013Pubmed ID
24308268Pubmed Central ID
PMC3926756DOI
10.1021/bi401080kScopus ID
2-s2.0-84891510210 (requires institutional sign-in at Scopus site) 28 CitationsAbstract
Apolipoprotein AI (apoA-I) is the principal acceptor of lipids from ATP-binding cassette transporter A1, a process that yields nascent high density lipoproteins. Analysis of lipidated apoA-I conformation yields a belt or twisted belt in which two strands of apoA-I lie antiparallel to one another. In contrast, biophysical studies have suggested that a part of lipid-free apoA-I was arranged in a four-helix bundle. To understand how lipid-free apoA-I opens from a bundle to a belt while accepting lipid it was necessary to have a more refined model for the conformation of lipid-free apoA-I. This study reports the conformation of lipid-free human apoA-I using lysine-to-lysine chemical cross-linking in conjunction with disulfide cross-linking achieved using selective cysteine mutations. After proteolysis, cross-linked peptides were verified by sequencing using tandem mass spectrometry. The resulting structure is compact with roughly four helical regions, amino acids 44-186, bundled together. C- and N-terminal ends, amino acids 1-43 and 187-243, respectively, are folded such that they lie close to one another. An unusual feature of the molecule is the high degree of connectivity of lysine40 with six other lysines, lysines that are close, for example, lysine59, to distant lysines, for example, lysine239, that are at the opposite end of the primary sequence. These results are compared and contrasted with other reported conformations for lipid-free human apoA-I and an NMR study of mouse apoA-I.
Author List
Pollard RD, Fulp B, Samuel MP, Sorci-Thomas MG, Thomas MJAuthors
Mary Sorci Thomas PhD Professor in the Medicine department at Medical College of WisconsinMichael J. Thomas PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
Amino Acid MotifsAnimals
Apolipoprotein A-I
Humans
Mice
Models, Molecular
Protein Binding
Protein Folding
Protein Structure, Secondary
