• 1 January 1977
    • journal article
    • research article
    • Vol. 3  (3) , 153-162
Abstract
C[cyclic]AMP- and cGMP-dependent protein kinases were purified from mammalian and non-mammalian sources. Each enzyme demonstrated high specificity and affinity for the cyclic nucleotide with binding of 2 mol of nucleotide per holoenzyme and each enzyme was an ATP:phosphotransferase. The holoenzymes have similar MW and demonstrated similar molecular asymmetry. A structural model relating the 2 enzymes was proposed. cGMP-dependent protein kinase was proposed to be a dimer composed of 2 identical protomers in isologous association with the chains arranged in anti-parallel fashion. cAMP-dependent protein kinase was proposed to have a similar structure with a dyad axis of symmetry but with a discontinuity in each chain. These structures account for the differing mechanisms of cyclic nucleotide activation of the 2 enzymes.

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