Penta-EF hand, calcium binding motifs, found in grancalcin
Grancalcin (GCA) is a cytosolic Ca2+-binding protein specifically expressed in neutrophils and monocytes/macrophages. It displays a Ca2+-dependent translocation to granules and plasma membrane upon neutrophil activation, suggesting roles in granule-membrane fusion and degranulation of neutrophils. It may also play a role in the regulation of vesicle/granule exocytosis through the reversible binding of secretory vesicles and plasma membranes upon the presence of calcium. Moreover, GCA is involved in inflammation, as well as in the process of adhesion of neutrophils to fibronectin. It plays a key role in leukocyte-specific functions that are responsible for host defense, and affects the function of integrin receptors on immune cells through binding to L-plastin in the absence of calcium. Furthermore, GCA can strongly interact with sorcin to form a heterodimer, and further modulate the function of sorcin. GCA exists as homodimers in solution. It contains five EF-hand motifs attached to an N-terminal region of an approximately 50 residue-long segment rich in glycines and prolines. GCA binds two Ca2+ ions through its EF1 and EF3 hands.
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