Characterization of Human Copine III as a Phosphoprotein with Associated Kinase Activity
The copines, first described by Creutz et al. [(1998) J. Biol. Chem. 273, 1393−1402], comprise a two C2 domain-containing protein family and are known to aggregate phosphatidylserine membranes in a calcium-dependent manner. No enzymatic function has been attributed to copines yet. Due to a cross-rea...
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Published in | Biochemistry (Easton) Vol. 39; no. 42; pp. 13034 - 13043 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
24.10.2000
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Subjects | |
Online Access | Get full text |
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Summary: | The copines, first described by Creutz et al. [(1998) J. Biol. Chem. 273, 1393−1402], comprise a two C2 domain-containing protein family and are known to aggregate phosphatidylserine membranes in a calcium-dependent manner. No enzymatic function has been attributed to copines yet. Due to a cross-reacting activity of Mikβ1, an antibody to the IL-2Rβ chain, we were able to serendipitously purify, partially microsequence, and clone human copine III. The 5 kb copine III transcript is expressed ubiquitously as determined by a multitissue Northern blot analysis. Phosphoamino acid analysis revealed phosphorylation of copine III on serine and threonine residues. In vitro kinase assays were performed with immunoprecipitated endogenous copine III, chromatography-purified endogenous copine III, and recombinant copine III expressed in Saccharomyces cerevisiae. The exogenous substrate myelin basic protein was phosphorylated in all in vitro kinase assays containing copine III immunoprecipitate or purified copine III. A 60-kDa band was observed in corresponding in gel kinase assays with staurosporine-activated cells. Cell lines expressing high levels of copine III protein had correspondingly high kinase activity in copine III antiserum immunoprecipitate. However, the copine amino acid sequences lack the traditional kinase catalytic domain. Therefore, the data suggest copine III may possess an intrinsic kinase activity and represent a novel unconventional kinase family. |
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Bibliography: | istex:0BB90A5AFFD2B49C8529B0DA7EB712C6D31E0A69 This study was supported by National Institutes of Health Grants CA45225 and CA64906. The nucleotide sequence for human copine III reported in this paper has been submitted to GenBank under accession number AF077226. ark:/67375/TPS-M8T1DCK6-0 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-2960 1520-4995 |
DOI: | 10.1021/bi001250v |