title: Disruption of prosomes by some bivalent metal ions results in the loss of their multicatalytic proteinase activity and cancels the nuclease resistance of prosomal RNA.
abstract: Prosomes are ribonucleoprotein particles constituted by a variable set of about 20 proteins found associated with untranslated mRNA. In addition, they contain a small RNA, the presence of which has been an issue of controversy for a long time. The intact particles have a multicatalytic proteinase (MCP) activity and are very stable; we have never observed autodigestion of the particle by its intrinsic proteinase activity. Surprisingly it was found that Zn2+ and Cu2+ ions at concentrations of 0.1-1 mM disrupt the prosome particles isolated from HeLa cells and duck erythroblasts and abolish instantaneously its MCP activity, without altering the two-dimensional electrophoretic pattern of the constituent proteins. Fe2+, however, seems to induce autodegradation rather than dissociation of the prosome constituents. Most interestingly, protein or oligopeptide substrates protect the particle and its proteinase activity from disruption by Zn2+ or Cu2+. Nuclease-digestion assays reveal that the prosomal RNA, which is largely resistant in the intact particle, becomes digestible after dissociation of prosomes by Zn2+. These data give, for the first time, unambiguous proof of the presence of an RNA in the particle. Furthermore, they demonstrate a structure-function relationship between the complex and its enzyme activity, which seems to be based on the particle as an entity and not on the single constituent proteins.
authors.affiliation: Institut Jacques Monod, Université Paris, France.
authors.forename: H G
authors.initials: HG
authors.lastname: Nothwang
authors.forename: O
authors.initials: O
authors.lastname: Coux
authors.forename: F
authors.initials: F
authors.lastname: Bey
authors.forename: K
authors.initials: K
authors.lastname: Scherrer
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent; D003300:Copper / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004372:Ducks; D004591:Electrophoresis, Polyacrylamide Gel; D005296:Ferrous Compounds / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008670:Metals / Q000494:pharmacology*; D009097:Multienzyme Complexes / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D012333:RNA, Messenger / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism*; D013045:Species Specificity; D013379:Substrate Specificity; D015032:Zinc / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D005296:Ferrous Compounds; D008670:Metals; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D003300:Copper; D012260:Ribonucleases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008274:Magnesium; D015032:Zinc; D002118:Calcium