The binding and activation of Nitric Oxide Synthase by modified central linker and “phosphomimetic” Calmodulin proteins

Abstract

Calmodulin (CaM) is a ubiquitous calcium‐binding protein that is known to interact and regulate hundreds of intercellular functional proteins. The promiscuity of CaM is partially due to its highly flexible central linker region that separates its two terminal domains which interact with its target protein. Modification of the central linker region of CaM can result in changes in the proximity of the two terminal domains, their relative orientation, binding affinity and activation of the CaM target proteins. The present study was designed to investigate the role of the central linker of CaM by introducing select mutations, including phosphomimetic residues, into the CaM central linker region. The effects of these modifications on the binding and activation of the three mammalian nitric oxide synthase (NOS) isozymes have been investigated using biophysical techniques including circular dichroism, FTIR and gel shift mobility assays. Assays have been performed to assess the effect that modified CaM linker residues have on NOS enzyme activation and electron transfer. This research is supported by NSERC (J.G.G.)