Sarcoplasm calcium binding protein (SARC)

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Sarcoplasm calcium binding protein (SARC) binds three Ca2+ or Mg2+ ions competitively. It is found both as a monomer and as a dimer; it may function as a calcium buffer. Neither the sequences of its four EF-hands nor of the three interdomain linkers closely resemble other EF- hands or linkers. Crystal structures are available of SARC from the sandworm, Nereis diversicolor, [68] and from amphioxus, Branchiostoma lanceolatum, [69]. Although the sequences share only 22% overall identity, the main chain traces of the two are nearly superimposable. All four domains have Ca2+ bound. The hydrophobic faces of lobes 1,2 and 3,4 contact one another.