Biophysical analysis of the dynamics of calmodulin interactions with neurogranin and Ca 2+ /calmodulin-dependent kinase II
Seeger C, Talibov V, Danielson U
Journal of Molecular Recognition
2017 (February) pp: e2621
Calmodulin (CaM) functions depend on interactions with CaM-binding proteins, regulated by math formula . Induced structural changes influence the affinity, kinetics, and specificities of the interactions. The dynamics of CaM interactions with neurogranin (Ng) and the CaM-binding region of math formula/calmodulin-dependent kinase II (CaMKII290−309) have been studied using biophysical methods. These proteins have opposite dependencies for CaM binding. Surface plasmon resonance biosensor analysis confirmed that math formula and CaM interact very rapidly, and with moderate affinity (). Calmodulin-CaMKII290−309 interactions were only detected in the presence of math formula, exhibiting fast kinetics and nanomolar affinity (). The CaM–Ng interaction had higher affinity under -depleted ( and k−1 = 1.6 × 10−1s−1) than -saturated conditions (). The IQ motif of Ng (Ng27-50) had similar affinity for CaM as Ng under math formula-saturated conditions (), but no interaction was seen under -depleted conditions. Microscale thermophoresis using fluorescently labeled CaM confirmed the surface plasmon resonance results qualitatively, but estimated lower affinities for the Ng () and CaMKII290−309() interactions. Although CaMKII290−309 showed expected interaction characteristics, they may be different for full-length CaMKII. The data for full-length Ng, but not Ng290−309, agree with the current model on Ng regulation of math formula /CaM signaling.