The third cupredoxin domain of CopA copper resistance protein family
CopA is a multicopper oxidase (MCO) related to laccase and L-ascorbate oxidase, both copper-containing enzymes. It is part of the copper-regulatory cue operon, which employs a cytosolic metalloregulatory protein CueR that induces expression of CopA and CueO under copper stress conditions. CopA is a copper efflux P-type ATPase that is located in the inner cell membrane and is is involved in copper resistance in bacteria. CopA mutant causes a loss of function including copper tolerance and oxidase activity and copA transcription is inducible in the presence of copper. Although MCOs have diverse functions, majority of them have three cupredoxin domain repeats that include one mononuclear and one trinuclear copper center. The copper ions are bound in several sites: Type 1, Type 2, and/or Type 3. The ensemble of types 2 and 3 copper is called a trinuclear cluster. MCOs oxidize their substrate by accepting electrons at a mononuclear copper center and transferring them to the active site trinuclear copper center. The cupredoxin domain 3 of 3-domain MCOs contains the Type 1 (T1) copper binding site and part the trinuclear copper binding site, which is located at the interface of domains 1 and 3.
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