The conformation of the 1: 1 complex of protoporphyrin IX and apomyoglobin was studied by circular dichroism, potentiometric titration, and reaction with bromoacetate. Circular dichroism studies indicate that protoporphyrin and heme similarly affect the o-helix content of apomyoglobin. The apparent number of normal imidazoles in the protoporphyrin-apomyoglobin complex, as judged by reactivity t...
