Knowledge Bank

Cellular calcium either directly controls, or at a minimum modulates nearly, if not, all human functions. As such, the structural motif that forms the calcium binding pocket (EF-hand) is one of the most common protein elements found in Mammalia. The calcium binding properties of the EF-hands appear to be "tuned" to receive and respond to different calcium signals and can vary by over 6 orders of magnitude. Our laboratory is attempting to understand the rules that govern calcium binding to proteins, so that we might be able to engineer these proteins as gene therapies to treat diseases. Calmodulin is a small, switch-like, calcium binding protein that plays multiple roles in all human cells depending on what protein system it is attached. We are using rational design, super computers as well as evolutionary clues to help us engineer calmodulins with specific functionalities. Using a simple mathematical model to describe the calcium binding events of calmodulin and available steady-state and kinetic data, we determined the exact rate parameters that govern this interaction for wild type calmodulin and other variants (such as plant calmodulins, disease mutants, and engineered calmodulins). Troponin C is the "cousin" of calmodulin and is very important in the calcium regulation of muscle contraction. Using a previously created mathematical model for the activation of the cardiac troponin complex, we modified the rate parameters to effectively simulate the calcium binding data for the slow skeletal isoform and characterized the effects of a potential small molecule therapeutic. This information better helps us identify what we want to alter in order to achieve a particular outcome (in terms of engineering novel calmodulins) and may help explain the different responses between cardiac and slow skeletal troponin.