title: Structure and functions of arthropod proteasomes.
abstract: Recent work on structural/functional relationships in arthropod proteasomes is reviewed. Taking advantage of our ability to induce a stable, proteolytically-active conformation of the lobster proteasome, the structures of basal and heat-activated complexes were probed with exogenous proteases. Increased sensitivity to chymotrypsin and trypsin showed that heat activation induced a more 'open' conformation, allowing entry of large substrates into the catalytic chamber. In Drosophila, the effects of two developmental mutant alleles (DTS-7 and DTS-5) encoding proteasome subunits (Z and C5, respectively) on the subunit composition and catalytic activities of the enzyme were examined. Both qualitative and quantitative differences in compositions between wild-type (+/+) and heterozygotes (+/DTS) indicated that incorporation of mutant subunits alters post-translational modifications of the complex. Catalytic activities, however, were similar, which suggests that the developmental defect involves other proteasome properties, such as intracellular localization and/or interactions with endogenous regulators. A hypothetical model in which DTS subunits act as poison subunits is presented.
authors.affiliation: Department of Biology, Colorado State University, Fort Collins 80523, USA. don@lamar.colostate.edu
authors.forename: D L
authors.initials: DL
authors.lastname: Mykles
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D004330:Drosophila / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism*; D008121:Nephropidae / Q000201:enzymology*; D046988:Proteasome Endopeptidase Complex; D013329:Structure-Activity Relationship
chemical_list: D009097:Multienzyme Complexes; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases