title: Regulation of calcineurin phosphatase activity by its autoinhibitory domain.
abstract: The Ca(2+)-dependent activation of calcineurin phosphatase activity is regulated by an autoinhibitory element (residues 457-482) located 43 residues COOH-terminal of the calmodulin-binding domain (residues 390-414). Removal of residues 457-482 does not result in full Ca(2+)/calmodulin-independent activity. Full activity in the absence of Ca(2+) requires the removal of residues 420-457. In the present study the presence of additional autoinhibitory elements within residues 420-457 was tested using two calcineurin A subunit COOH-terminal region constructs containing residues 420-511 (AI(420-511)) or 328-511 (AI(328-511)). Using recombinant, Ca(2+)/calmodulin-independent calcineurin, AI(420-511) and AI(328-511) were three- to fourfold more potent inhibitors of calcineurin phosphatase activity than the synthetic calcineurin autoinhibitory peptide(457-482). Calmodulin reversed the inhibition of calcineurin phosphatase activity by AI(328-511) but not AI(420-511). Kinetic studies indicated that AI(420-511) exhibited mixed-type inhibition and that the enzyme/substrate/inhibitor complex is partially active. These results indicate that (i) additional autoinhibitory elements are present within residues 420-457, (ii) calmodulin-binding to the autoinhibitory domain neutralizes the inhibitory function of the 420-457 autoinhibitory segment, (iii) the full-length autoinhibitory domain is a mixed-type inhibitor of calcineurin phosphatase activity, and (iv) the enzyme/substrate/inhibitor complex is partially catalytically active.
authors.affiliation: Vollum Institute, Oregon Health Sciences University, 3181 Southwest Sam Jackson Park Road, Portland, Oregon, 97201, USA. perrino@physio.unr.edu
authors.forename: B A
authors.initials: BA
authors.lastname: Perrino
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002417:Cattle; D004791:Enzyme Inhibitors / Q000737:chemistry; D015870:Gene Expression; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015202:Protein Engineering; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D002147:Calmodulin; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; C120817:calcineurin phosphatase; D010744:Phosphoric Monoester Hydrolases; D002118:Calcium