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PubMed · 8530352

A proteasome activator subunit binds calcium.

C Realini·M Rechsteiner
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Abstract

We recently cloned a cDNA encoding the 29-kDa subunit of human red blood cell regulator (REG), a potent activator of the multicatalytic protease (Realini, C., Dubiel, W., Pratt, G., Ferrell, K., and Rechsteiner, M. (1994) J. Biol. Chem. 269, 20727-20732). The sequence of this subunit contains 28 "alternating" lysine and glutamic acid residues (a KEKE motif). Similar regions are present in a number of Ca(2+)-binding proteins, and using standard filter assays, the recombinant protein is shown to bind 45Ca2+ and ruthenium red. 45Ca2+ is also bound to a ubiquitin extension protein containing the 28-residue KEKE region from the 29-kDa REG subunit. Thus, the 29-kDa REG subunit is a Ca(2+)-binding protein, and its KEKE region is able to bind divalent cations. Ca2+ reversibly inhibits the enhanced peptidase activity of complexes between the multicatalytic protease and recombinant REG. This raises the possibility that multicatalytic protease activity is regulated by calcium in vivo.

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Amino Acid SequenceBinding SitesCalciumCalcium-Binding ProteinsCysteine EndopeptidasesElectrophoresis, Polyacrylamide GelEnzyme ActivationErythrocytesHumansKineticsMacromolecular SubstancesMagnesiumMolecular Sequence DataMultienzyme ComplexesProteasome Endopeptidase ComplexProteinsRecombinant ProteinsJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.

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C Realini, M Rechsteiner. 1995-12-15. A proteasome activator subunit binds calcium.. https://doi.org/10.1074/jbc.270.50.29664

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