title: Isolation by calcium-dependent translation to neutrophil-specific granules of a 42-kD cytosolic protein, identified as being a fragment of annexin XI.
abstract: Secretion of neutrophil granules is dependent on calcium, but at the same time this process is regulated differently for each type of granules. We attempted to find calcium-regulated proteins that selectively translocate from the cytosol to the membranes of the neutrophil granules. An in vitro calcium-dependent translocation assay was designed by mixing cytosol with different neutrophil organelles isolated by subcellular fractionation. Immunoblotting using an anti-cytosol antiserum revealed a cytosolic protein of 42 kD that selectively binds to the specific granules of human neutrophils. It was neither associated with the azurophil granules nor with the secretory vesicles/plasma membrane. The protein was translocated at a calcium concentration of 100 micromol/L and binding was further increased by 1 mmol/L calcium. The 42-kD protein was partially purified from neutrophil cytosol by using its affinity for specific granules and by ion-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the partly purified protein allowed the 42-kD band to be excised and subjected to tryptic peptide mapping. Peptides from three peaks were N-terminally sequenced. Searching among known proteins, each one of the amino acid sequences was found to share sequence similarity to annexin XI.
authors.affiliation: Phagocyte Research Laboratory, Department of Medical Microbiology and Immunology, University of Göteborg, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Sjölin
authors.forename: C
authors.initials: C
authors.lastname: Dahlgren
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017302:Annexins / Q000737:chemistry* / Q000276:immunology; D001692:Biological Transport; D002118:Calcium / Q000502:physiology*; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007106:Immune Sera; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009504:Neutrophils / Q000378:metabolism* / Q000648:ultrastructure; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D010449:Peptide Mapping; D011817:Rabbits; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D017302:Annexins; D007106:Immune Sera; D010446:Peptide Fragments; D002118:Calcium