Analysis of copper-induced metallothionein expression using autonomously replicating plasmids in Candida glabrata.

Candida glabrata strains and a stable plasmid were developed that were suitable for analysis of copper-inducible expression from promoters of the three metallothionein (MT) genes. The two homologous MTII genes, MTIIa and MTIIb, encode the same polypeptide but are differentially induced by copper salts. MTIIb is more highly inducible than MTIIa and cells harboring a single MTIIb exhibit a greater resistance to copper salts compared to cells harboring a single MTIIa. The differential copper inducibility was mapped to sequences between -03 and -292 upstream of the MT coding sequences. Expression of MTI is highly Cu-regulated, but this MT gene confers much less resistance than MTII genes.