Molecular cloning and expression analyses of mouse ss klotho, which encodes a novel Klotho family protein

We report here the identification of mouse beta klotho (beta kl), which enc odes a type I membrane protein with high resemblance to Klotho (KL). Both b eta KL and KL consist of two internal repeats with homology to family 1 gly cosidases, while these essential glutamates for the enzymatic activities we re not conserved. The identical pattern of substitution and variation in th e substituted amino acids between these two proteins indicate that they lik ely to form a unique family within the glycosidase family 1 superfamily. Du ring mouse embryonic development, strong beta kl expression was detected in the yolk sac, gut, brown and white adipose tissues, liver and pancreas, an d in the adult, predominantly in the liver and pancreas. Despite the high s tructural similarity between beta KL and KL, their expression profiles were considerably different and beta kl expression was not induced in kl-defici ent mouse mutants. (C) 2000 Elsevier Science Ireland Ltd. All rights reserv ed.