1991 Volume 110 Issue 4 Pages 532-540
The three-dimensional structure of cytochrome c3 from Desulfovibrio vulgaris Hildenbor-ough has been determined by use of the molecular replacement method and refined at 2.0 Å resolution. A suitable crystal of the cytochrome c3 was obtained from buffer solution (25 mM Tris-HC1, pH 7.4), with 75% ethanol as the precipitating reagent. Crystallographic data are as follows: α=43.17 Å, b=62.91 Å, c=41.17 Å, orthorhombic, P212121 and Z 4. Constrained least-squares refinement and a molecular dynamics procedure with a simulat-ed structure annealing method yielded a crystallographic R-factor of 0.212. The similarity in the folding pattern of both cytochromes c3 is established, the mean deviation of the polypeptide backbone between the two structures being 0.367 Å. Most of the amino acids substitutions from DvMF were located on the surface of the molecule, and in particular, S27 and V86 were placed near the propionic acid of the heme group so as to hang over the heme and the cleft of the molecule.