title: Conformational changes of hemoproteins as evidenced by second derivative spectroscopy of aromatic amino acids.
abstract: Based on a comparison of the 2nd derivative spectra of cytochrome P-450 LM2, cytochrome c and hemoglobin with the corresponding mixtures of aromatic amino acids and the individual aromatic amino acids a significant red shift of the maxima of the absorption bands appearing as distinct minima in the 2nd derivative spectrum have been observed in the proteins. This red shift has been shown to be caused by a lowered polarity of the immediate surroundings of the chromophores. The band positions of the aromatic amino acids in the 3 investigated hemoproteins are nearly the same and therefore do not allow to qantitate conformation dependent spectral changes of the chromophores. In agreement with X-ray crystallographic data aromatic amino acids of cytochrome c and of hemoglobin are subjected to spectral changes at the transition from the oxidized to the reduced state. These redox linked conformational changes are indicated by significant changes of the amplitudes of the aromatic acids in the 2nd derivative spectrum. A quantitative evaluation of the amplitudes revealed characteristics specific for cytochrome c and hemoglobin. Surprisingly the 2nd derivative spectrum in the median UV-region of cytochrome P-450 LM2 does not show any significant change at reduction.
mesh_terms: D000328:Adult; D000596:Amino Acids; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification; D003574:Cytochrome c Group / Q000302:isolation & purification; D006454:Hemoglobins / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008862:Microsomes, Liver; D010649:Phenylalanine; D011487:Protein Conformation; D011817:Rabbits; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan; D014443:Tyrosine
chemical_list: D000596:Amino Acids; D003574:Cytochrome c Group; D006454:Hemoglobins; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; D003577:Cytochrome P-450 Enzyme System