A molecular mechanism for copper transportation to tyrosinase that is assisted by a metallochaperone, caddie protein

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The Cu(II)-soaked crystal structure of tyrosinase in a complex with a protein, designated “caddie”, which has previously determined by us, displays to possess two copper ions at the catalytic center. We observed two copper-binding sites in the caddie protein, speculating that the copper bound to caddie may be transported to the tyrosinase catalytic center. In the present study, at the 1.16 to 1.58 A resolution, we determined the crystal structures of tyrosinase complexed with a caddie prepared by altering the soaking time of the copper ion and the structures of tyrosinase complexed with a few mutants of a caddie which displays no or little ability to activate tyrosinase. Based on these structures, we propose a molecular mechanism to transport two copper ions to the tyrosinase catalytic center, which is assisted by a caddie as a metallochaperone.