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

We report here the identification of mouse beta klotho (beta kl), which encodes a type I membrane protein with high resemblance to Klotho (KL). Both beta KL and KL consist of two internal repeats with homology to family 1 glycosidases, while these essential glutamates for the enzymatic activities were not conserved. The identical pattern of substitution and variation in the substituted amino acids between these two proteins indicate that they likely to form a unique family within the glycosidase family 1 superfamily. During mouse embryonic development, strong beta kl expression was detected in the yolk sac, gut, brown and white adipose tissues, liver and pancreas, and in the adult, predominantly in the liver and pancreas. Despite the high structural similarity between beta KL and KL, their expression profiles were considerably different and beta kl expression was not induced in kl-deficient mouse mutants. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.