Overview:

The second messenger cyclic AMP (cAMP) activates cAMP-dependent protein kinase (PKA or cAPK) in mammalian cells and controls many cellular mechanismssuch as gene transcription, ion transport and protein phosphorylation (1). Inactive PKA is a heterotetramer composed of a regulatory subunit (R) dimer and a catalytic subunit (C) dimer, and in this inactive state, the pseudosubstrate sequences on the R subunits block the active sites on the C subunits. Three C subunit isoforms (-cα, -cβand -cγ) and two families of regulatory subunits (RI and RII) with distinct cAMP binding properties have been identified. Upon binding of cAMP to the R subunits, the autoinhibitory contact is eased and active monomeric C subunits are released.

References:

1. Montminy M: Transcriptional regulation by cyclic AMP. Annu Rev Biochem, 1997;66:807-22.