Functional and conformational properties of the exclusive C-domain from the Arabidopsis copper chaperone (CCH)

The Arabidopsis thaliana copper chaperone (CCH) is a small copper binding p rotein involved in copper trafficking. When compared to homologues from oth er eukaryotes, CCH has two different domains; the conserved N-domain and th e plant-exclusive C-domain, a C-terminal extension with an unusual amino-ac id composition. In order to characterize this extra C-domain, the CCH prote in, the N-domain and the C-domain were all expressed separately in heterolo gous systems. While the N-domain retained the copper chaperone and antioxid ant properties described for the yeast Atx1 and human HAH1 counterparts, th e C-domain displayed particular structural properties that would be necessa ry to optimize copper homoeostasis in plant cells where it could be respons ible for the metallochaperone plant-exclusive intercellular transport. The whole CCH protein and the C-domain, but not the N-domain, displayed altered SDS/PAGE mobilities. CD spectroscopy showed that the N-domain fold is repr esentative of an alpha/beta protein, while the C-domain adopts an extended conformation.