To examine in vivo phosphorylation of lipocortin I we made use of a polyclonal antibody to an amino terminal peptide of lipocortin I. This antibody does not recognize any other member of the annexin protein family, and can both immunoprecipitate lipocortin I and recognize this protein on western blots. Using cleaved forms of lipocortin I, we have been able to demonstrate that protein kinase C phosphorylates this protein in vitro within the first 29 amino terminal amino acids. However, the addition of phorbol esters to A431 cells over a wide range of concentrations and for varying periods of time did not stimulate the phosphorylation of this protein. Since in vitro lipocortin I is an excellent substrate for all three isoforms, alpha, beta, gamma, of protein kinase C, the discrepancy in these finding is not secondary to the presence of varying forms of this protein kinase within different cell types.
|Original language||English (US)|
|Number of pages||6|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Apr 28 1989|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology