Lobster Muscle Proteasome and the Degradation of Myofibrillar Proteins

Abstract

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

The 26S Proteasome in Garlic (Allium sativum): Purification and Partial Characterization

“…Effect of Protease Inhibitors on the 26S Proteasome from Garlic Cloves. The hydrolysis of [methyl- 14 C] R-casein (13.6 mM, 8.4 Bq), with or without protease inhibitors, was performed as previously described (19) except that MES (MES-KOH), pH 5.5 (the observed pH optimum for this substrate), at a final concentration of 23.3 mM was substituted for the tris buffer. Each assay contained 15 µg of purified proteasome in a reaction volume of 75 µL.…”

“…The 26S/20S proteasome has been identified in archaebacteria and eubacteria (12) and many species in the animal [Xenopus (7), human (10), rat (13), lobster (14), and Drosophila (15)], fungi [yeast (8)], and plant [spinach (16,17), rice, and carrot (18)] kingdoms.…”

“…As a general interest, we expanded our work to plant proteases. We detected proteolytic activity using an extract of garlic cloves as the source of enzyme and [methyl- 14 C] R-casein as the substrate (unpublished). Our interest in this plant grew due to its presumed therapeutic role in various diseases (21).…”

Ubiquitin- and proteasome-dependent pathway of protein degradation as an emerging therapeutic target

“…Myofibrillar proteins in the muscles are degraded mainly by the ubiquitin-proteasome pathway, probably after some initial calpain-mediated cleavages [158][159][160]. Moreover, it has been noted that components of the ubiquitin-proteasome pathway are activated during conditions accompanied with increased muscular proteolysis [157,161].…”

Molecular Regulation of Muscle Growth in Crustacea

“…The claw muscle in this crab atrophies prior to ecdysis by as much as 30-60% to allow the muscle to pass through the narrow basi-ischium joint at the base of the cheliped (Skinner, 1966;Mykles & Skinner, 1982. The biochemical basis of this protein degradation has been studied by Mykles (1992Mykles ( , 1993 with calcium dependent proteinases, or calpains being identified and their actions characterized (Mattson & Mykles, 1993). As a result of this large premoult atrophy, claw muscle sarcomeric units are predominantly added during the postmoult period.…”