Effect of 2-mercaptoethanol on the electrophoretic behavior of rat and dogfish metallothionein and chromatographic evidence of a naturally occurring metallothionein polymerization.

1. Metallothionein behavior in SDS-PAGE has been characterized. 2. It has been found that metallothionein behavior in this electrophoretic system depends upon the reducing environment. Migration as a well-defined protein band is only achieved in the presence of 2-100 mM 2-mercaptoethanol. 3. Within those 2-mercaptoethanol levels, both rat and dogfish metallothionein migrate as a protein with a molecular weight several times higher than that expected by amino acid analyses. This is not due to molecule oxidations, since this effect is promoted by the presence of 2-mercaptoethanol. 4. No effect of 2-mercaptoethanol on metallothionein behavior is found in conventional PAGE. 5. The present results suggest that to study the effect of 2-mercaptoethanol in SDS-PAGE is a simple and accurate way to identify a protein as metallothionein. 6. It has also been found that metallothionein aggregates naturally in the absence of ionic strength.