Molecular Cloning of Mammalian 28,000 M_r Vitamin D-Dependent Calcium Binding Protein (Calbindin-D_28K): Expression of Calbindin-D_28K RNAs in Rodent Brain and Kidney

We report the isolation of a cloned cDNA for the mammalian 28,000 M_r vitamin D-dependent calcium binding protein (calbindin-D_28K; CaBP_28K) by immunological screening of a λgt11 bacterial expression library. The library contained cDNAs copied from poly(A)RNA of adult mouse cerebellum. We confirmed the identity of the CaBP_28K cDNA by comparing its DNA sequence with that of chick CaBP_28K cDNA. In the coding region, 79% of the mouse cDNA sequence was identical to the reported sequence of CaBP_28K cDNA derived from chicken intestine. Rat brain and kidney each contain three species of poly(A)RNA that hybridize to CaBP_28K cDNA–a major species of 1.9 kb, and rarer components of 2.8 kb and 3.2 kb. All three RNAs appear to be transcribed from a single gene. The ratios of these CaBP_28K RNAs were the same in brain and kidney. In the cerebellum, in situ hybridization reveals that CaBP_28K RNAs are confined to Purkinje neurons.