The EF hand is a helix-loop-helix structural domain (motif) found in a large family of calcium-binding proteins. The HGNC 'EF-hand domain containing' (super)family contains 219 genes. Subfamilies within the superfamily include the actinins, the SPARC family and the S100 protein family. Other proteins that contain EF-hand motifs include some of the calmodilins, calpains, calcium voltage-gated channel subunits, the diacylglycerol kinases, myosin light chains and some of the solute carrier family (SLC) transporters.

S100 family members are found only in vertebrates. There are 14 S100 genes in the human genome which produce at least 21 different proteins, which have been detected both intracellularly and in secreted forms. S100 proteins are involved in the regulation of various cellular processes including cell cycle progression, differentiation, endocytosis and exocytosis, apoptosis, and cancer metastasis [1]. Many of the family members are used as diagnostic markers across a range of disease areas including cardiac disease, cancer, neurological disease and inflammation [2-3].

1. Donato R, Cannon BR, Sorci G, Riuzzi F, Hsu K, Weber DJ, Geczy CL. (2013) Functions of S100 proteins. Curr Mol Med, 13 (1): 24-57. [PMID:22834835]

2. Medkova A, Srovnal J, Potomkova J, Volejnikova J, Mihal V. (2018) Multifarious diagnostic possibilities of the S100 protein family: predominantly in pediatrics and neonatology. World J Pediatr, 14 (4): 315-321. [PMID:29858979]

3. Šumová B, Cerezo LA, Szczuková L, Nekvindová L, Uher M, Hulejová H, Moravcová R, Grigorian M, Pavelka K, Vencovský J et al.. (2019) Circulating S100 proteins effectively discriminate SLE patients from healthy controls: a cross-sectional study. Rheumatol Int, 39 (3): 469-478. [PMID:30392117]