GCA, also known as Grancalcin, is calcium-binding protein that is especially abundant in human neutrophils. It belongs to the penta EF-hand (PEF) subfamily of EF-hand proteins, which also comprises calpain, sorcin, peflin, and ALG-2. This protein undergoes important conformational changes upon binding of calcium, which subsequently exposes hydrophobic amino acid residues, which direct the protein to hydrophobic surfaces. It interacts with L-plastin, a protein known to have actin bundling activity, which suggests that GCA may play a role in the regulation of neutrophils adhesion.