Figure 1.

(A) Ratios of Zn(II) (black) and Cu(I) (gray) to protein domains after limited proteolytic digestion of Zn₆E_c-1 incubated with 0, 1, or 2 equiv. of Cu(I); (B) UV–VIS spectra of fractions from size exclusion chromatography (SEC) containing the γ- (solid line) or β_E-E_c-1 domain (dotted line) obtained after proteinase K cleavage of the Zn₆E_c-1 species which was incubated with 1 equiv. of Cu(I). The shoulder around 260 nm is assigned to the S → Cu(I) charge transfer transitions and only observed for the γ-E_c-1 domain.