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Determination of the methionine haem ligand conformation in cytochrome c H from Methylophilus methylotrophus by two‐dimensional 1 H NMR
Author(s) -
Santos Helena,
Turner David L.
Publication year - 1993
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260311318
Subject(s) - chemistry , crystallography , stereochemistry , ligand (biochemistry) , cytochrome c , cytochrome , proton , physics , quantum mechanics , biochemistry , receptor , mitochondrion , enzyme
A complete relaxation matrix approach was used to determine the conformation of the Met ligand to the haem in Methylophilus methylotrophus cytochrome c H , including the configuration at the sulphur; the pattern of NOEs is shown to be dominated by spin diffusion at mixing times as short as 25 ms, rendering the two‐spin approximation unreliable. The Met conformation, together with an analysis of aromatic proton resonances, indicates a structure almost identical with that found by x‐ray crystallography for Pseudomonas aeruginosa cytochrome c 551 , which has a 45% similarity in sequence. The paramagnetic shifts of the haem methyl proton resonances in the oxidized protein support the view that the asymmetry in the electronic structure of the haem is dominated by the orientation of the Met ligand.