Localization of the regulatory subunit of cAMP-dependent protein kinase in Saccharomyces cerevisiae.

The subcellular distribution of the regulatory subunit of cAMP-dependent protein kinase in Saccharomyces cerevisiae cells was determined by subcellular fractionation and indirect immunofluorescence microscopy using the bcy1 mutant deficient in the regulatory subunit as control. The regulatory subunit of cAMP-dependent protein kinase showing cAMP-binding activity was identified as a single protein of 50 kDa by photoaffinity labeling and immunoblotting. The regulatory subunit was concentrated in a nuclear fraction in addition to a cytoplasmic fraction. By comparison of the regulatory subunit distribution with the DNA localization, the area detected by the indirect immunofluorescence was identified as the nucleus.