Heteronuclear NMR studies of human serum apolipoprotein A-I. Part I. Secondary structure in lipid-mimetic solution.

The apolipoprotein A-I (apoA-I) solution structure in the presence of sodium dodecyl sulfate (SDS) was determined by combination of chemical shift index and torsion angle likelihood obtained from shift and sequence similarity methods. ApoA-I in lipid-mimetic solution is composed of alpha-helices (residues 8-32, 45-64, 67-77, 82-86, 90-97, 100-118, 122-140, 146-162, 167-205, 210-216 and 221-239), with 2-5 residue irregular segments between helical repeats, and the irregular segment 78-81 within helical repeat 2. ApoA-I is a monomer in the SDS complex and no evidence of interhelical interactions is found. Comparison of the apoA-I and apoA-I(1-186) [Okon et al., FEBS Lett. 487 (2001) 390-396] solution structures revealed that apoA-I undergoes a conformational change around Pro121.