Multiple conformations at functional site of hemerythrin: Evidence from resonance Raman spectra

Abstract

Resonance Raman spectra were obtained for monomeric oxymyohemerythrin and for the azide, thiocyanate, cyanate, cyanide and fluoride adducts of metmyohemerythrin. The internal ligand vibrations in these complexes appear at essentially the same frequencies as those in the corresponding complexes of octameric hemerythrin. Likewise the Fe-O frequencies in H216O do not depend on quaternary structure of the protein. The anionic adducts fall into 2 classes in regard to isotope exchange behavior in H218O. They also manifest a novel photochemical transformation from one class of exchange behavior to the other. The functional site in hemerythrin probably exists in at least 2 different conformational states and irradiation can stimulate isotope exchange in the exchange-resistant form.