Detection of metallothionein isoforms from three different species using on-line capillary electrophoresis mass spectrometry

An on-line capillary electrophoresis-mass spectrometry method (CE-MS) for t he detection of metallothionein (MT) isoforms is described. The detected ma sses were usually within 1-1.5 mass units of the expected molecular weights . MT-containing samples from rabbit, sheep, and yeast (Saccharomyces cerevi siae) were subjected to CE-MS analysis. The analysis of rabbit liver MT rev ealed the masses of 10 proteins/peptides. Five of the detected masses corre sponded well with the expected masses calculated from the amino acid sequen ce of previously described MT isoforms, one was suspected to be a deacetyla ted form of MT-2A, one was presumed to be a yet unknown isoform, and three masses were classified as non-MT compounds. From the analysis of a fetal sh eep liver extract six proteins were detected of which three masses correspo nded to previously described MT isoforms. Two purified MT subforms from S. cerivisiae (encoded by the CUP1 locus) were analyzed for their copper conte nt and both forms were found to contain eight copper atoms per molecule. (C ) 1998 Academic Press.