Calcium-dependent binding of sorcin to the N-terminal domain of synexin (annexin VII).

The annexins are characterized by their ability to bind phospholipid membranes in a Ca2+-dependent manner. Sequence variability between the N-terminal domains of the family members may contribute to the specific cellular function of each annexin. To identify proteins that interact with the N-terminal domain of synexin (annexin VII), a fusion ...
protein was constructed composed of glutathione S-transferase fused to amino acids 1-145 of human synexin. Affinity chromatography using this construct identified sorcin as a Ca2+-dependent synexin-binding protein. Overlay assays confirmed the interaction. The glutathione S-transferase construct associates with recombinant sorcin over the range of pCa2+ = 4.7-3.1 with no binding observed at pCa2+ = 5.4. Overlay assays using deletion constructs of the synexin N-terminal domain mapped the sorcin binding site to the N-terminal 31 amino acids of the synexin protein. Additionally, synexin forms a complex with sorcin and recruits this protein to chromaffin granule membranes in a Ca2+-dependent manner. Sorcin is able to inhibit synexin-mediated chromaffin granule aggregation in a manner saturable with increasing sorcin concentrations, but does not influence the Ca2+ sensitivity of synexin-mediated granule aggregation. Therefore, the interaction between sorcin and synexin may serve to regulate the functions of these proteins on membrane surfaces in a Ca2+-dependent manner.
Mesh Terms:
Adrenal Medulla, Amino Acid Sequence, Animals, Annexin A7, Binding Sites, Calcium, Calcium-Binding Proteins, Cattle, Chromaffin Granules, Humans, Mice, Molecular Sequence Data, Molecular Weight, Neoplasm Proteins, Phosphoproteins, Protein Binding, Recombinant Proteins, Xenopus
J. Biol. Chem.
Date: Aug. 29, 1997
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