H-1-NMR STUDY OF THE STRUCTURAL INFLUENCE OF Y64 SUBSTITUTION IN DESULFOVIBRIO-VULGARIS HILDENBOROUGH CYTOCHROME C(553)

Y64 has been replaced in cytochrome c(553) from Desulfovibrio vulgaris Hildenborough by phenylalanine, leucine, valine, serine and alanine r esidues. An NMR study of structural variation induced in both oxidored uction states of the molecule has been carried out by analysing observ ed chemical-shift variations. Dynamic changes were evidenced using NH exchange. We have observed that the substitution has a drastic effect on the stability of the molecule in the reduced state, although there is no effect on the reduction potential of the cytochrome. Y64 --> F s ubstitution induces particular effects on the NH exchange at the N-ter minal, C-terminal and central alpha-helices and increases the stabilit y of the oxidized molecule.