Calcium (Ca+2 or Ca) is the most abundant cation and it is required for many physiological activities such as bone formation and it acts as a second messenger in signal transduction. However only 1% of Ca is present in ionic form in biological fluids. Ca concentration is regulated by calcitropic hormones that act on bone, kidney, and intestine. Extracellular Ca+-levels are sensed and regulated by Calcium Sensing receptor (CASR). When Ca levels are limiting then it must be taken up by active, transcellular pathways comprising (1) Ca++ entry across apical membrane, (2) cytosolic transport of Ca++ across the cell form apical to basolateral membrane facilitated by a family of low mol wt Calcium binding proteins (CABPs) that include vitamin D3-dependent Ca++ binding proteins (calbindin-D9k, Calbindin-28k, Calretinin, Parvalbumin, S100, calmodulin) and finally (3) an active extrusion of Ca++ through basolateral membrane mediated by Ca++-ATPase and Na+-Ca++ exchangers (NCX). Ca++ absorption in intestine and its reabsorption in kidney are carried out by Ca++ Transport (CaT) proteins, CaT-1, CaT-2 or Epithelial Ca Channel (ECAC1/ECAC2/CaT-Like (CaT-L) proteins.

Calbindins are Ca-binding proteins belonging to the troponin C superfamily. There are two types of CaBPs: the "trigger"- and the "buffer"-CaBPs. The conformation of "trigger" type CaBPs changes upon Ca2+ binding and exposes regions on protein that interact with target molecules, thus altering their activity. The buffer-type CABP are thought to control the intracellular calcium concentration. CABP9K (CALB3 or CABP1; mouse, rat, and human 79 aa; chromosome Xp; ~9kD) is a cytosolic Ca-binding protein initially found in rat pancreas. It is also expressed in intestine, placenta, uterus and kidney. Its expression is controlled by vitamin D and sex hormone in a tissue specific manner. In keeping with its role in Ca-transport, its expression is highest in duodenal villus enterocytes. It is further shown that CABP9K is only expressed in differentiated enterocytes. CABP9K gene also contains Cdx2-homeoprotein binding sites, and that Cdx2 may play a crucial role in CABP9K transcription.

Human synthetic peptide

Highly purified

As reported

Supplied as a liquid in PBS, pH 7.2

The peptide is 78% conserved in mouse, rat, bovine and porcine D9K

This product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications without the expressed written authorization of United States Biological.