Klotho Beta (KLb)

KLb encodes a 1,043-amino acid protein that shares 41.2% identity with mouse Kl. Like Kl, Klb contains an N-terminal signal sequence, followed by 2 tandemly repeated glycosidase-like domains, a C-terminal transmembrane domain, and a short cytoplasmic tail. Both Kl and Klb lack 2 key glutamates in the predicted active centers of the glycosidase-like domains.

Northern blot analysis of adult mouse tissues showed that Klb was predominantly expressed in liver and pancreas, with lower levels in skin and weak expression in stomach, skeletal muscle, small intestine, and lung. In mouse embryos, Klb expression became detectable at day 11 and increased in intensity as development progressed. In situ hybridization of mouse embryos revealed strong Klb expression in yolk sac, gut, brown and white adipose tissue, liver, and pancreas.