Specific sequences in the N and C termini of apolipoprotein A-IV modulate its conformation and lipid association.
Apolipoprotein (apoA-IV) is a 376-residue exchangeable apolipoprotein that may play a number of important roles in lipid metabolism, including chylomicron assembly, reverse cholesterol transport, and appetite regulation. In vivo, apoA-IV exists in both lipid-poor and lipid-associated forms, and the balance between these states may determine its function. We examined the structural elements that modulate apoA-IV lipid binding by producing a series of deletion mutants and determining their ability to interact with phospholipid liposomes. We found that the deletion of residues 333-343 strongly increased the lipid association rate versus native apoA-IV. Additional mutagenesis revealed that two phenylalanine residues at positions 334 and 335 mediated this lipid binding inhibitory effect. We also observed that residues 11-20 in the N terminus were required for the enhanced lipid affinity induced by deletion of the C-terminal sequence. We propose a structural model in which these sequences can modulate the conformation and lipid affinity of apoA-IV.
Pearson
Kevin
K
Department of Pathology and Laboratory Medicine, The University of Cincinnati, Cincinnati, Ohio 45237-0507, USA.
Tubb
Matthew R
MR
Tanaka
Masafumi
M
Zhang
Xiu Qi
XQ
Tso
Patrick
P
Weinberg
Richard B
RB
Davidson
W Sean
WS
D000595:Amino Acid Sequence; D001054:Apolipoproteins A / Q000737:chemistry* / Q000235:genetics*; D002784:Cholesterol / Q000378:metabolism; D002914:Chylomicrons / Q000737:chemistry; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008074:Lipoproteins / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D009821:Oils / Q000737:chemistry; D010649:Phenylalanine / Q000737:chemistry; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000737:chemistry
D001054:Apolipoproteins A; D002914:Chylomicrons; D008055:Lipids; D008074:Lipoproteins; D008081:Liposomes; D009821:Oils; C022205:apolipoprotein A-IV; D014867:Water; D010649:Phenylalanine; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine