Identification and functional expression of ctaA, a P-type ATPase gene involved in copper trafficking in Trametes versicolor

Abstract

Here the identification and characterization of a gene encoding a copper-trafficking enzyme, ctaA (copper-transporting ATPase), from the basidiomycete Trametes versicolor are described. This P-type copper ATPase gene has two alleles, differing primarily in the length of the second, unusually long intron, and encodes a 983 aa protein with 40 % sequence identity to yeast Ccc2p. Overexpression of ctaA in yeast grown in the presence of copper led to a 15-fold increase in laccase yields, while overexpression of ctaA and tahA, a previously identified copper homeostasis gene of T. versicolor, was additive, leading to a 20-fold increase in laccase production. In T. versicolor, overexpression of ctaA and tahA led to an eightfold increase in laccase expression, and a cotransformant still expressed laccase at 3000 μM copper when hardly any laccase activity is detected in the wild-type strain. Apparently, at low to moderate levels of copper tahA and ctaA overexpression disturbs the normal hierarchy of copper distribution, resulting in more being directed to the Golgi, while with high copper amounts that normally switch on the copper detoxification processes, tahA and ctaA gene products seem to out-compete the metallothionein copper chaperones, meaning laccase is still supplied with copper. These results may lead to a better understanding of copper trafficking and the hierarchy of copper distribution in the cell, and possibly be useful for constructing laccase-overproducing strains for biotechnological purposes.