Structure and functions of arthropod proteasomes

• Published in: Molecular biology reports 1999-04, Vol.26 (1/2), p.103-111
• Main Author: Mykles, D.L
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - chemistry; Adenosine Triphosphatases - metabolism; Animals; Arthropoda; Cysteine Endopeptidases - chemistry; Cysteine Endopeptidases - metabolism; Drosophila; Drosophila - enzymology; Drosophila melanogaster; Enzymes; Homarus americanus; insects; Marine; Multienzyme Complexes - chemistry; Multienzyme Complexes - metabolism; Nephropidae - enzymology; Proteasome Endopeptidase Complex; proteinases; Structure-Activity Relationship; ubiquitin
• ISSN: 0301-4851; 1573-4978
• DOI: 10.1023/A:1006976524916

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.