Paper Citing NAMD - Abstract
Gursky, Olga; Jones, Martin K.; Mei, Xiaohu; Segrest, Jere P.; Atkinson, David
Structural basis for distinct functions of the naturally occurring Cys mutants of human apolipoprotein A-I
JOURNAL OF LIPID RESEARCH, 54:3244-3257, DEC 2013
HDL removes cell cholesterol and protects against atherosclerosis. ApoA-I provides a flexible structural scaffold and an important functional ligand on the HDL surface. We propose structural models for apoA-I-Milano (R173C) and apoA-I-Paris (R151C) mutants that show high cardioprotection despite low HDL levels. Previous studies established that two apoA-I molecules encircle HDL in an antiparallel, helical double-belt conformation. Recently, we solved the atomic structure of lipid-free Delta(185-243) apoA-I and proposed a conformational ensemble for apoA-I-WT on HDL. Here we modify this ensemble to understand how intermolecular disulfides involving C173 or C151 influence protein conformation. The double-belt conformations are modified by belt rotation, main-chain unhinging around Gly, and Pro-induced helical bending, and they are verified by comparison with previous experimental studies and by molecular dynamics simulations of apoA-I-Milano homodimer. In our models, the molecular termini repack on various-sized HDL, while packing around helix-5 in apoA-I-WT, helix-6 in apoA-I-Paris, or helix-7 in apoA-I-Milano homodimer is largely conserved. We propose how the disulfide-induced constraints alter the protein conformation and facilitate dissociation of the C-terminal segment from HDL to recruit additional lipid. Our models unify previous studies of apoA-I-Milano and demonstrate how the mutational effects propagate to the molecular termini, altering their conformations, dynamics, and function.
