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. Author manuscript; available in PMC: 2018 Jul 6.
Published in final edited form as: Biochem J. 2017 Jul 6;474(14):2389–2403. doi: 10.1042/BCJ20160969

Figure 3. Cyclic nucleotide binding of individual CNB domains.

Figure 3

Competition curves were derived from SPR experiments as exemplified in Figure 2 (normalized data). (A) Binding competition of PKA hRIα CNB-A (residues 115–274). Cyclic AMP and cyclic IMP bind to CNB-A with high nanomolar affinities, while cGMP binds with a micromolar affinity. CNB-A shows a more than 30-fold preference for cAMP. (B) CNB-B (residues 234–381) has a significantly higher affinity for cAMP compared with CNB-A, but still binds cGMP with micromolar affinity, resulting in an 110-fold selectivity. Cyclic IMP is bound with an intermediate affinity between cAMP and cGMP.