MITOCHONDRIAL CARBONIC-ANHYDRASE (ISOZYME-V) IN MOUSE AND RAT - CDNA CLONING, EXPRESSION, SUBCELLULAR-LOCALIZATION, PROCESSING, AND TISSUE DISTRIBUTION

When the human cDNA, isolated on the basis of homology to the murine c arbonic anhydrase (CA) ''Y'' was expressed in COS cells, the human CA was targeted to and processed in mitochondria, as expected for CA-V. H owever, tissue distribution reported for the corresponding mouse CA Y mRNA was much more limited than that reported for the distribution of CA-V immunostaining in rat tissues. To determine whether the murine cD NA actually encodes a mitochondrial CA activity and to compare the tis sue distribution of the homologous murine and rat gene products, we us ed reverse transcription-PCR to reisolate the murine CA-V candidate cD NA and used the murine cDNA probe to isolate the homologous rat cDNA. We compared the two cDNA sequences, the activities they expressed afte r transfection of COS cells, and the sites of N-terminal processing of expressed products. In addition, we used antibodies to the C-terminal peptides predicted from each cDNA to compare distribution of CA-V in mouse and rat tissues and to identify CA-Vs in mitochondria isolated f rom mouse and rat liver. From these studies, we conclude that bath mou se and rat CA-V candidate cDNAs encode active CAs that are targeted to and processed in mitochondria and that there are real differences in tissue distribution of CA-V between mouse and rat. However, the findin gs that the M(r) of CA-V in fat tissues is smaller than that previousl y reported and that the tissue distribution also differs lead us to co nclude that the antibody used in prior reports most likely misidentifi ed another antigen in rat tissues as CA-V.