Reactions and interconversion of met and dimer hemocyanin.

The regenerable methemocyanin of $\text{Busycon canaliculatum}$ is shown to be EPR-nondetectable. The small EPR signal present in met preparations is a nonregenerable binuclear cupric unit accounting for ～ 6% of the active sites. A variety of anions are found to bind to met with the reactions being complicated by both reduction and competitive binding of buffer. The metastable dimer hemocyanin is shown to rearrange either directly to EPR-nondectable met or through an EPR-detectable regenerable binuclear cupric form obtained on reaction of dimer hemocyanin with azide. These results combined with previous results on half met derivatives are used to support the presence of an endogenous protein bridge between the two coppers in hemocyanin.