Dependence on pH of Structural and Dynamical Changes of a Calmodulin Domain Mutant

Abstract: Calmodulin (CaM) is a highly conserved protein able to bind Ca2+. When Ca2+ is bound the protein can bind and activate further proteins with several individual functions. CaM switches to a more open conformation when Ca2+-bound and is able to do so at a high rate. Little is known about the conformational switches between apo and Ca2+-bound states. A hypothesis suggests that protonation/deprotonation of a histidine side-chain is part of the answer and thus the dynamics of CaM would be pH dependent. This was further investigated in this thesis. Methods to carry out the project included protein expression of isotope labelled CaM-TR2C E140Q, standard protein purification and protein adapted Nuclear Magnetic Resonance (NMR) spectroscopy. The results suggest that CaM-TR2C E140Q is likely to depend on pH and that histidine 107 (H107) may have a central role in the conformational changes observed. At lower pH it was also suggested that CaM-TR2C E140Q obtained a more open conformation with weakened intramolecular interactions and that the tertiary structure of CaM-TR2C E140Q may have been disrupted.