Crystal structure and electroi CueO, a multicopper oxidase copper homeostasis in Esche

CueO (YacK), a multicopper oxidase, is part of the copper-reguladi, tory cue operon in Escherichia coli. The crystal structure of CueO th has been determined to 1.4-A resolution by using multiple anomlo] alous dispersion phasing and an automated building procedure sir that yielded a nearly complete model without manual intervention. This is the highest resolution multicopper oxidase structure th yet determined and provides a particularly clear view of the four re coppers at the catalytic center. The overall structure is similar to 1. those of laccase and ascorbate oxidase, but contains an extra M 42-residue insert in domain 3 that includes 14 methionines, nine of "b which lie in a helix that covers the entrance to the type I (T1, blue) co copper site. The trinuclear copper cluster has a conformation not II] previously seen: the Cu-O-Cu binuclear species is nearly linear th (Cu-O-Cu bond angle = 170?) and the third (type II) copper lies only el 3.1 A from the bridging oxygen. CueO activity was maximal at pH Sc 6.5 and in the presence of >100 /LM Cu(ll). Measurements of ox intermolecular and intramolecular electron transfer with laser flash