Calbindin 3 (CALB3)

Calbindin D9K, the vitamin D-dependent calcium-binding protein (CaBP9K), was first described in rat intestine.The intestinal protein is vitamin D-dependent and its expression correlates with calcium transport activity. In keeping with its role in calcium absorption, concentrations of CaBP9K are highest in duodenal villus enterocytes. A vitamin D-independent role in calcium transport in placenta and kidney has been postulated. The clones included a coding region of 79 amino acids, 57-nucleotide 5-prime- and 159-nucleotide 3-prime noncoding regions, and a poly(A) tail. The deduced protein sequence is homologous to other mammalian calbindins. Northern analysis revealed the mRNA in human duodenum to be about 600 nucleotides long. Expression levels in adult human tissue were substantially lower than in child, rat, or porcine intestine.