Biological Activity: PKA regulatory subunit alpha specifically inhibits PKA catalytic subunit (Ki about 0.1nM). Activity can be restored by adding cAMP (Kact about 100nM). The binding of the catalytic subunit is dependent on the presence of ATP and Mg. Physical Appearance: Sterile Filtered clear solution. Unit Definition: One unit is defined as the amount of recombinant PKA catalytic subunit alpha, required to incorporate 1nmol of phosphate into the specific substrate peptide kemptide (LRRASlG) in one minute at 30 C. PKA regulatory subunit I a Recombinant is a dimeric 90 kDa protein.
PKAR-I alpha is purified by proprietary chromatographic techniques.
The Regulatory (R) subunit of Protein Kinase A (PKA) inhibits its kinase activity by shielding the Catalytic (C) subunit from physiological substrates. This inhibition is reversed in response to extra-cellular signals that increase cAMP levels in the cytoplasm. Upon cAMP binding to R, C is allosterically released from R, activating a spectrum of downstream signaling cascades. Crystallographic data indicated that a series of distinct conformational changes within CBD-A must occur to relay the cAMP signal from the cAMP binding site to the R:C interaction interface. One critical cAMP relay site within the CBD-A of R has been identified as Asp170 because the D170A mutation selectively reduces the negative cooperativity between the cAMP- and C-recognition sites (i.e. the KD for the R:C complex in the presence of cAMP is reduced by more than 12-fold), without significantly compromising the high affinity of R for both binding partners.
Subunit: The inactive form of the enzyme is composed of two regulatory chains and two catalytic chains. Activation by cAMP produces two active catalytic monomers and a regulatory dimer that binds four cAMP molecules. PRKAR1A also interacts with RFC2; the complex may be involved in cell survival (By similarity). Interacts with AKAP4.
Ptm: The pseudophosphorylation site binds to the substrate-binding region of the catalytic chain, resulting in the inhibition of its activity (By similarity).
Miscellaneous: Two types of regulatory chains are found: type I, which predominates in skeletal muscle, and type II, which predominates in cardiac muscle (By similarity).
Similarity: Belongs to the cAMP-dependent kinase regulatory chain family.
Similarity: Contains 2 cyclic nucleotide-binding domains.