Copper(II) protoporphyrin IX as a reporter group for the heme environment in myoglobin

Abstract

Copper(II) protoporphyrin IX was introduced into [sperm whale] apomyoglobin, and its utility as a reporter group of the heme environment was examined. The Soret and visible absorption bands and ESR spectrum showed that the Cu(II) was 5 coordinate, probably through coordination to the F-8 proximal histidine. The resonance Raman spectrum did not indicate any appreciable distortion from the solution conformation of copper(II) protoporphyrin IX dimethyl ester in CS2. The UV circular dichroism showed no alteration of helical content of the globin from that of metmyoglobin. Circular dichroism of the porphyrin transitions suggests that packing of the amino acid side chains around the porphyrin was different than that in native metmyoglobin.