Reticulocalbin 1(RCN1) is a calcium-binding protein. It binds calcium and may regulate calciumdependent activities in the endoplasmic reticulum lumen or post-ER compartment. The protein contains six conserved regions with similarity to a high affinity Ca(+2)-binding motif, the EF-hand. High conservation of amino acid residues outside of these motifs, in comparison to mouse reticulocalbin, is consistent with a possible biochemical function besides that of calcium binding.