A new spatial structure for the axial methionine observed in cytochrome c5 from Pseudomonas mendocina. Correlations with the electronic structure of heme c

摘要: Cytochrome c5 from Pseudomonas mendocina has been isolated and the coordination geometry at heme iron was investigated by 1H nuclear magnetic resonance circular dichroism spectroscopy. Individual assignments were obtained for c axial ligands. From studies of Overhauser enhancements histidine imidazole ring orientation relative to group found coincide with that other c-type cytochromes. In contrast, a new structure observed methionine. This include S chirality iron-bound sulfur atom, but compared cytochromes c-551 Pseudomonads Rhodopseudomonas gelatinosa, which also contain S-chiral methionine, spatial arrangement γ-and β-methylene groups α carbon methionine is markedly different. Analysis electron spin density hypothesis electronic primarily governed sp3 lone-pair orbital atom respect plane.