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( R P )‐cAMPS inhibits the cAMP‐dependent protein kinase by blocking the cAMP‐induced conformational transition
Author(s) -
Dostmann Wolfgang R.G.
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)01201-o
Subject(s) - protein subunit , protein kinase a , tryptophan , chemistry , gamma subunit , mole , recombinant dna , transition (genetics) , biophysics , microbiology and biotechnology , kinase , biochemistry , biology , amino acid , gene
( R P )‐cAMPS is known to inhibit competitively the cAMP‐induced activation of cAMP‐dependent protein kinase (PKA). The molecular nature of this inhibition, however, is unknown. By monitoring the intrinsic tryptophan fluorescence of recombinant type I regulatory subunit of PKA under unfolding conditions, a free energy value ( ΔG D H2O ) of 8.23 ± 0.22 was calculated. The cAMP‐free form of the regulatory subunit was less stable with ΔG D H2O = 6.04 ± 0.05 kcal/mol. Native stability was recovered by treatment of the cAMP‐free protein with either cAMP or ( S P )‐cAMPS but not with ( R P )‐cAMPS. Thus, ( R P )‐cAMPS binding to the regulatory subunit keeps the protein in a locked conformation, unable to release the catalytic subunit. This finding was further supported by demonstrating that holoenzyme formation was greatly accelerated only when bound cAMP was replaced with ( R P )‐cAMPS but not with cAMP or ( S P )‐cAMPS.