Crystallographic structure refinement of Chromatium high potential iron protein at two Angstroms resolution.

摘要: The structure of Chromatium high potential iron protein (HiPIP) has been refined by semiautomatic Fo-Fc (observed minus calculated amplitude Fourier methods to a convential R index, R=sum the absolute value divided sum Fo, 24.7% for model in which bond distances and angles are constrained standard values. Bond length angle constraints were applied only intermittenly during computations. At late stage refinement, atomic parameters Fe4S4 cluster plus 4 associated cystein S-gamma atoms adjusted least squares kept fixed rest refinement. consists 625 632 nonhydrogen 75 water molecules. Seven side chain could not be located final electron density map. A computer program rather than visual inspection was used wherever possible refinement: locating molecules, removing molecules that too closely approach other atoms, deleting lay regions low density, evaluating progress refinement is sufficiently economical routinely crystal determinations. complete HiPIP required approximately 12 hours CDC 3600 time cost less $3000 starting from "trial structure," based upon multipe isomorphoous replacement phases, gave an 43%...