Klotho beta, a divergent structural member of the glycosidase I superfamily, is expressed primarily in the liver and pancreas, with lower expression in adipose tissue. Like Klotho, Klotho beta facilitates binding between FGF19 subfamily members and their receptors via formation of a ternary complex. The Klotho beta mediated interaction of human FGF19 (mouse FGF15) with FGF Receptor 4 in the liver negatively regulates bile acid synthesis by controlling the secretion of two key bile acid synthase genes, cholesterol 7-alpha hydroxylase (Cyp7a1) and sterol 12-alpha hydroxylase (Cyp8b1). Klotho beta is also a cofactor for the interaction of FGF21 with FGF Receptor 1c in adipocytes, which allows FGF21 to stimulate GLUT1 expression, upregulating adipocyte insulindependent glucose uptake. The 1043aa type I transmembrane protein is composed of a 51aa signal sequence, a 943aa extracellular domain (ECD) containing two glycosidase-like regions, a 21aa transmembrane domain, and 28aa intracellular tail. Since Klotho-related proteins lack critical active site Glu residues present in beta-glycosidases, it was initially unclear whether they were functional enzymes. However, glucuronidase activity has since been demonstrated for Klotho, indicating that physiologically relevant enzymatic activity for Klotho beta is also possible. The extracellular domain shares 79%, 87%, 87% and 67% identity with mouse, equine, canine and rat Klotho beta, respectively. The low identity with rat reflects aa discordance within rodent ECD.
Recombinant protein corresponding to Phe53-Leu997 from human Klotho beta, with a C-terminal 10-His tag expressed in NSO cells. Swiss/UniProt Accession: Q86Z14.
SDS-PAGE:113-125kD, reducing conditions
Activity:Measured by its binding ability in a functional ELISA.
Specific Activity:When Recombinant human FGF-21 is immobilized at 1ug/ml (100ul/well) Recombinant human Klotho B His-tag binds with an ED50 of 2.5-20ng/ml
Storage and Stability:Aliquot to avoid repeated freezing and thawing and store at -70°C. Aliquots are stable for 6 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.
