Exp Mol Med.  2001 Mar;33(1):32-36.

Effect of metal ions on the stability of metallothionein in the degradation by cellular fractions in vitro

• Hahn SH
• Yoo OJ
• Gahl WA

Abstract

Metallothioneins (MT), small molecular weight metal binding proteins are known to play an important protective role against heavy metal toxicity, either as antioxidants or pre-oxidants. However, the mode of metabolic fate of MTs in various metal complexes is not clearly understood. This study was carried out to better understand the mode of selective turnover rate of various form of MT in complexes with different metals. The degradation of in vitro translated mouse 35S-cysteine-MT was examined in lysosomal or cytosolic fractions from mouse liver by gel electrophoresis and autoradiography. Overnight incubations of MT showed extensive proteolysis in the lysosomal fraction but not in cytosolic fractions. However, Cu2+-MT was found to be stable under the same experimental condition. In contrast, Zn did not interfere with MT degradation. These results suggest that lysosomes are chiefly responsible for MT removal and appears to be selective on the metals involved in the MT complex. In vitro, translated, radiolabeled MT provides a suitable substrate for investigating the characteristics of MT degradation.

Keyword

metallothionein; lysosome; degradation; copper; zinc

MeSH Terms

Animal
Copper/*metabolism/pharmacology
Ions
Liver/drug effects/*metabolism
Lysosomes/metabolism
Metallothionein/drug effects/*metabolism
Mice
Sulfur Radioisotopes
Support, Non-U.S. Gov't
Zinc/*metabolism/pharmacology