Incorporation of Copper Ions into T2 T3 Centers of Two Domain Laccases

Laccase belongs to the family of copper containing oxidases. A study was made of the mechanism that sustains the incorporation of copper ions into the T2 T3 centers of recombinant two domain laccase Streptomyces griseoflavus Ac 993. The occupancy of the T3 center by copper ions was found to increase with an increasing copper content in the culture medium and after dialysis of the protein preparation against a copper sulfate containing buffer. The T2 center was filled only when overproducer strain cells were grown at a higher copper concentration in the medium. Two domain laccases were assumed to possess a channel that serves to deliver copper ions to the T3 center during the formation of the three dimensional laccase conformation and dialysis of the protein preparation. A narrower channel leads to the T2 center in two domain laccases compared with three domain ones, rendering the center less accessible for copper atoms. The incorporation of copper ions into the T2 center of two domain laccases is likely to occur in the course of their biosynthesis or the formation of a functional trime