Secondary structure of human apolipoprotein A-I(1-186) in lipid-mimetic solution

The solution structure of an apoA-I deletion mutant, apoA-I(1-186) was dete rmined by the chemical shift index (CSI) method and the torsion angle likel ihood obtained from shift and sequence similarity (TALOS) method, using het eronuclear multidimensional NMR spectra of [u-C-13, u-N-15, u-50% H-2]apoA- I(1-186) in the presence of sodium dodecyl sulfate (SDS), The backbone reso nances mere assigned from a combination of triple-resonance data (HNCO, HNC A, HN(CO)CA, HN(CA)CO and HN(COCA)HA), and intraresidue and sequential NOEs (three-dimensional (3D) and four-dimensional (4D) C-13- and N-15-edited NO ESY). Analysis of the NOEs, H-alpha, C-alpha and C' chemical shifts shows t hat apoA-I(1-186) in lipid-mimetic solution is composed of ol-helices (whic h include the residues 8-32, 45-64, 67-77, 83-87, 90-97, 100-140, 146- 162, and 166-181), interrupted by short irregular segments. There is one relati vely long, irregular and mostly flexible region (residues 33-44), that sepa rates the N-terminal domain (residues 1-32) from the main body of protein. In addition, we report, for the first time, the structure of the N-terminal domain of apoA-I in a lipid-mimetic environment. Its structure (alpha -hel ix 8-32 and flexible linker 33-44) mould suggest that this domain is struct urally, and possibly functionally, separated from the other part of the mol ecule. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.