Multicatalytic proteinase complex (MCP) was studied in skeletal muscle of the hibernating ground squirrel, Spermophilus tridecemlineatus. MCP was partially purified using a S-400 gel filtration column and Centricon concentrating devices and assayed fluorometrically using three AMC-labeled substrates. Km and Vmax values were determined for each substrate with no significant differences between the enzyme from euthermic versus hibernating animals when assayed at 23°C. However, properties of MCP from euthermic and hibernating ground squirrels were differentially affected by low assay temperature (8-10°C) and also differed from the mouse enzyme, the data indicating that ground squirrel MCP is better suited for low temperature function. MCP preferentially degrades oxidatively-damaged proteins and quantification of protein carbonyl content showed that the level of oxidatively-damaged protein in skeletal muscle decreased by > 75% during hibernation suggesting a continuing role for the MCP in the torpid state.

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Keywords Carbonyl proteins, Metabolic rate depression, Oxidative damage, Proteasome, Protein degradation
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Journal Molecular and Cellular Biochemistry
Woods, A.K. (Ashley K.), & Storey, K. (2005). Effects of hibernation on multicatalytic proteinase complex in thirteen-lined ground squirrels, Spermophilus tridecemlineatus. Molecular and Cellular Biochemistry, 271(1-2), 205–213. doi:10.1007/s11010-005-6341-5