In molecular biology, the calcium-binding EGF domain is an EGF-like domain of about forty amino-acid residues found in epidermal growth factor (EGF). This domain is present in a large number of membrane-bound and extracellular, mostly animal, proteins.[1][2][3][4][5] Many of these proteins require calcium for their biological function and a calcium-binding site has been found at the N-terminus of some EGF-like domains.[6] Calcium-binding may be crucial for numerous protein-protein interactions.
For humancoagulation factor IX it has been shown that the calcium-ligands form a pentagonal bipyramid.[7] The first, third and fourth conserved negatively charged or polar residues are side chainligands. The latter is possibly hydroxylated.[6] A conserved aromatic residue, as well as the second conserved negative residue, are thought to be involved in stabilising the calcium-binding site.
As in non-calcium binding EGF-like domains, there are six conserved cysteines and the structure of both types is very similar as calcium-binding induces only strictly local structural changes.[6]
References
↑Davis CG (May 1990). "The many faces of epidermal growth factor repeats". New Biol. 2 (5): 410–9. PMID2288911.
↑Barker WC, Johnson GC, Hunt LT, George DG, Tsugita A (June 1986). "[Similar domains in different proteins: detection and significance]". Tanpakushitsu Kakusan Koso (in 日本語) (29 Suppl): 54–68. PMID3534958.
↑ 6.06.16.2Selander-Sunnerhagen M, Ullner M, Persson E, Teleman O, Stenflo J, Drakenberg T (September 1992). "How an epidermal growth factor (EGF)-like domain binds calcium. High resolution NMR structure of the calcium form of the NH2-terminal EGF-like domain in coagulation factor X". J. Biol. Chem. 267 (27): 19642–9. doi:10.2210/pdb1ccf/pdb. PMID1527084.