THE CUPREDOXIN FOLD IS FOUND IN THE SOLUBLE CU-A AND CYOA DOMAINS OF 2 TERMINAL OXIDASES

The CD spectra of the Cu-A domain from subunit II of Paracoccus cytoch rome c oxidase and the CyoA domain of subunit II from E. coli quinol o xidase have been recorded in the wavelength region 260-185 nm. A compu ter program based on a set of CD spectra of proteins with known struct ures, and employing the stastistical method of variable selection, has been used to estimate the distribution of five forms of secondary str ucture. The analysis was improved by including the CD spectra of azuri n and plastocyanin in the basis set. For the Cu-A domain, an estimate from the primary structure was also made. The results show that the so luble domains have the cupredoxin fold, with very little helical struc ture and a predominance of beta-strands. The CyoA domain is very simil ar to azurin, but the beta-structure in the Cu-A protein resembles tha t in plastocyanin.