title: Role of the amino-terminal domain in regulating interactions of annexin I with membranes: effects of amino-terminal truncation and mutagenesis of the phosphorylation sites.
abstract: Phosphorylation of the N-terminal tail by protein kinase C strongly inhibits the ability of bovine or human annexin I to aggregate chromaffin granules by increasing the calcium requirement 4-fold (Wang, W., & Creutz, C. E. (1992) Biochemistry 31, 9934-9936). In the present study three forms of human annexin I truncated in the amino terminus at residue Trp-12, Lys-26, or Lys-29 exhibit dramatic differences in their sensitivities to calcium in a chromaffin granule aggregation assay, while the [Ca2+](1/2)max values for binding of the truncated proteins to granule membranes are similar. Cleavage at Trp-12 causes a 3-fold decrease in calcium sensitivity in the membrane aggregation assay, while cleavage at Lys-26 causes a 4-fold enhancement of calcium sensitivity. In contrast, cleavage at Lys-29 results in virtually no change in calcium sensitivity. Mutagenic substitution with negatively charged amino acids of Ser-27, a site for phosphorylation by protein kinase C, or Tyr-21, a site for phosphorylation by the epidermal growth factor receptor kinase, mimics the inhibition of granule-aggregating activity seen with phosphorylation by protein kinase C. When bovine chromaffin cells are stimulated to secrete by nicotine, annexin I is phosphorylated in the amino terminus. Thr-24 and Ser-28, which are sites for phosphorylation by protein kinase C in vitro, are two of the sites phosphorylated in vivo in stimulated chromaffin cells. These data demonstrate that the ability of annexin I to promote membrane aggregation is highly sensitive to changes in the structure of the N-terminal domain of the protein.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Microbiology, University of Virginia School of Medicine, Charlottesville 22908.
authors.forename: W
authors.initials: W
authors.lastname: Wang
authors.forename: C E
authors.initials: CE
authors.lastname: Creutz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017305:Annexin A1 / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D002154:Calpain / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism; D002417:Cattle; D002837:Chromaffin Granules / Q000187:drug effects / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000737:chemistry / Q000302:isolation & purification; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae
chemical_list: D017305:Annexin A1; D017931:DNA Primers; D010748:Phosphopeptides; D011994:Recombinant Proteins; D011493:Protein Kinase C; D002154:Calpain; D002402:Cathepsin D