Conformation of two peptides corresponding to human apolipoprotein C-I residues 7-24 and 35-53 in the presence of sodium dodecyl sulfate by CD and NMR spectroscopy.
Peptides corresponding to the proposed lipid-binding domains of human apolipoprotein C-I, residues 7-24 (ALDKLKEFGNTLEDKARE) and 35-53 (SAKMREWFSETFQKVKEKL), were studied by CD and two-dimensional 1H NMR spectroscopy. Sodium dodecyl sulfate (SDS) was used to model the lipoprotein environment. Analysis of the CD data shows that both peptides lack well-defined structure in aqueous solution but adopt helical, ordered structures upon the addition of SDS. The helical nature of the peptides in the presence of SDS was confirmed by H alpha secondary shifts. A total of 199 (apoC-I(7-24)) and 266 (apoC-I(35-53)) distance restraints were used in distance geometry and simulated annealing calculations to generate average structures for both peptides in aqueous solutions containing SDS. The backbone (N, C alpha, C = O) RMSD from the average structure of an ensemble of 20 structures was 0.73 +/- 0.22 and 0.48 +/- 0.14 A for apoC-I(7-24) and apoC-I(35-53), respectively. In the presence of SDS, the distance geometry and simulated annealing calculations show that both peptides adopt well-defined amphipathic helices with distinct hydrophobic and hydrophilic faces. The calculated structures are discussed relative to predicted structures. Comparing our CD and NMR results for the apoC-I fragments in SDS with CD results of others obtained in the presence of dimyristoylphosphatidylcholine indicates that SDS may be a better model of the lipoprotein environment.
Rozek
A
A
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
Buchko
G W
GW
Cushley
R J
RJ
D000595:Amino Acid Sequence; D053302:Apolipoprotein C-I; D001056:Apolipoproteins C / Q000737:chemistry*; D001665:Binding Sites; D002942:Circular Dichroism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008961:Models, Structural; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000302:isolation & purification; D011487:Protein Conformation; D012967:Sodium Dodecyl Sulfate
D053302:Apolipoprotein C-I; D001056:Apolipoproteins C; D010446:Peptide Fragments; D012967:Sodium Dodecyl Sulfate