Regucalcinis a highly conserved, calcium-binding protein, that is preferentially expressed in the liver and kidney. It may have an important role in calcium homeostasis. Studies in rat indicate that this protein may also play a role in aging, as it shows age-associated down-regulation. This gene is part of a gene cluster on chromosome Xp11.3-Xp11.23. Alternative splicing results in two transcript variants having different 5' UTRs, but encoding the same protein. Regucalcin is a proposed name for a calcium-binding protein that was discovered in 1978.Regucalcin differs from calmodulin and other Ca2+-related proteins as it does not contain an EF-hand motif of Ca2+-binding domain. It may regulate the effect of Ca2+ on liver cell functions.