Localization of catalytic and regulatory subunits of cyclic AMP-dependent protein kinases in mitochondria from various rat tissues.
Observation and quantification of the catalytic subunit C of cyclic AMP-dependent protein kinases by immuno-gold electron microscopy suggested a high concentration of cyclic AMP-dependent protein kinases in mitochondria from liver, kidney, heart and skeletal muscle, pancreas, parotid gland and brain cells. The position of gold particles pointed to a localization in the inner membrane/matrix space. A similar distribution was obtained by immunolocalization of the cyclic AMP-dependent protein kinase regulatory subunits RI and RII in liver, pancreas and heart cells. The results indicated the presence of both the type I and the type II cyclic AMP-dependent protein kinases in mitochondria of hepatocytes, and the preferential occurrence of the type I protein kinase in mitochondria from exocrine pancreas and heart muscle. The immunocytochemical results were confirmed by immunochemical determination of cyclic AMP-dependent protein kinase subunits in fractionated tissues. Determinations by e.l.i.s.a. of the C-subunit in parotid gland cell fractions indicated about a 4-fold higher concentration of C-subunit in the mitochondria than in a crude 1200 g supernatant. Immunoblot analysis of subfractions from liver mitochondria supported the localization in situ of cyclic AMP-dependent protein kinases in the inner membrane/matrix space and suggested that the type I enzyme is anchored by its regulatory subunit to the inner membrane. In accordance with the immunoblot data, the specific activity of cyclic AMP-dependent protein kinase measured in the matrix fraction was about twice that measured in whole mitochondria. These findings indicate the importance of cyclic AMP-dependent protein kinases in the regulation of mitochondrial functions.
Abteilung für Klinische Biochemie, Universität Göttingen, Federal Republic of Germany.
G
G
Schwoch
B
B
Trinczek
C
C
Bode
D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D007150:Immunohistochemistry; D007668:Kidney / Q000201:enzymology / Q000648:ultrastructure; D046911:Macromolecular Substances; D008297:Male; D008854:Microscopy, Electron; D008928:Mitochondria / Q000201:enzymology* / Q000648:ultrastructure; D008929:Mitochondria, Heart / Q000201:enzymology / Q000648:ultrastructure; D008930:Mitochondria, Liver / Q000201:enzymology / Q000648:ultrastructure; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013367:Submitochondrial Particles / Q000201:enzymology
D046911:Macromolecular Substances; D011494:Protein Kinases