Characterisation of rat 9-kDa cholecalcin (CaBP) messenger RNA using a complementary DNA. Absence of homology with 28-kDa cholecalcin mRNA.
The rat possesses two cholecalciferol-induced calcium-binding proteins, the cholecalcins (CaBP). The 9-kDa CaBP is mainly concentrated in the duodenum while 28-kDa CaBP is located in the kidney and cerebellum. The mRNA encoding 9-kDa CaBP has been characterised using the cloned cDNA, pC109, synthesised from rat duodenal 9-kDa CaBP mRNA [Desplan et al. (1983) J. Biol. Chem. 258, 13502-13505]. Nucleotide sequence analysis of this cDNA shows the presence of two stop codons, TGA and TAG, at positions 207 and 271, respectively, of the 3' untranslated region. The cDNA-hybridised mRNA, isolated from rat duodenum, directs the cell-free synthesis of two proteins precipitable by antisera to 9-kDa intestinal CaBP. A major protein comigrates with 9-kDa CaBP whereas a minor product corresponds to a protein which is larger by 2000 Da. The minor protein appears to result from read-through of the 'leaky' UGA stop signal. No protein band which was immunoprecipitable with 28-kDa CaBP antiserum was detected when cDNA-hybridized mRNA from rat kidney and cerebellum was translated in a cell-free system. Northern blots show that the cDNA pC109 sequence hybridizes to a homogeneous mRNA species 500-600 nucleotides long from rat duodenum. Larger mRNA species encoding 28-kDa CaBP are undetectable in rat kidney and cerebellum even under low stringency conditions. All these findings demonstrate that there is no cross-hybridisation between 9-kDa and 28-kDa CaBP mRNAs. Southern blot analysis of rat genomic DNA, that shows only one homologous 9-kDa gene, is consistent with these findings. Thus, all our data indicate that there are distinct genes coding for each rat cholecalcin.
D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics*; D002474:Cell-Free System; D002531:Cerebellum / Q000032:analysis; D003001:Cloning, Molecular; D003101:Collodion; D004247:DNA; D004386:Duodenum / Q000032:analysis; D004587:Electrophoresis, Agar Gel; D005796:Genes; D007668:Kidney / Q000032:analysis; D008099:Liver / Q000032:analysis; D008297:Male; D008970:Molecular Weight; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D012333:RNA, Messenger; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D064030:S100 Calcium Binding Protein G / Q000235:genetics*
D002135:Calcium-Binding Proteins; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; D003101:Collodion; D004247:DNA