Molecular characterization and immunolocalization of Dictyostelium discoideum protein phosphatase 2A

Protein phosphatase 2A (PP2A) was previously purified from Dictyostelium an d biochemically characterized. The purified PP2A holoenzyme was composed of a 37 kDa catalytic 'C-subunit', a 65 kDa 'A-subunit' and a 55 kDa 'B-subun it', We report here the characterization of the genes encoding the Dictyost elium PP2A subunits as well as the immunolocalization of the PP2A subunits in Dictyostelium. The cDNAs encoding the B- and C-subunits were isolated fr om a Dictyostelium library and the deduced amino acid sequences reveal stro ng conservation with the mammalian PP2A homologues, Southern blot analysis suggests that each of the PP2A subunit genes is present in a single copy. T he PP2A subunits were localized mainly to the cytosol in Dictyostelium cell s. However, immunofluorescence confocal microscopy demonstrates that the B- subunit of PP2A is highly enriched in centrosomes, suggesting a potential r ole for this PP2A regulatory subunit in the centrosomal function. (C) 1999 Federation of European Biochemical Societies.