Lobster muscle proteasome and the degradation of myofibrillar proteins.
The lobster proteasome is primarily a cytosolic enzyme in crustacean striated muscles, although a small amount (< 1% of total) occurs in aggregates associated with invaginations of the cell membrane. The complex exists in vitro in three distinct catalytic states (basal, SDS-activated, and heat-activated forms) which have identical subunit compositions. This review summarizes recent results showing that the branched-chain amino acid-preferring (BrAAP) activity mediates the hydrolysis of myofibrillar proteins by the heat-activated proteasome: (a) only the BrAAP activity is stimulated by heat treatment; (b) the BrAAP activity is strongly inhibited by protein substrates, and (c) both the BrAAP and proteolytic activities show similar sensitivities to cations and protease inhibitors.
Mykles
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Department of Biology, Colorado State University, Fort Collins 80523.
D000595:Amino Acid Sequence; D000818:Animals; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006358:Hot Temperature; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000196:embryology*; D008121:Nephropidae / Q000201:enzymology*; D009842:Oligopeptides / Q000737:chemistry; D046988:Proteasome Endopeptidase Complex; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013379:Substrate Specificity; D014336:Troponin / Q000378:metabolism; D014714:Vertebrates
D009097:Multienzyme Complexes; D009124:Muscle Proteins; D009842:Oligopeptides; D014336:Troponin; D012967:Sodium Dodecyl Sulfate; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex