Chemical shift assignments of calmodulin constructs with EF hand mutations

Abstract

Calmodulin (CaM) is a ubiquitous cytosolic Ca2+-binding protein able to bind and regulate hundreds of different proteins. It consists of two globular domains joined by a flexible central linker region. Each one of these domains contains two EF hand pairs capable of binding to Ca2+. Upon Ca2+ binding CaM undergoes a conformational change exposing hydrophobic patches that interact with its intracellular target proteins. CaM is able to bind to target proteins in the Ca2+-replete and Ca2+-deplete forms. To study the Ca2+-dependent/independent properties of binding and activation of target proteins by CaM, CaM constructs with Ca2+ binding disrupting mutations of Asp to Ala at position one of each EF hand have been used. One target protein of CaM is nitric oxide synthase, which catalyzes the production of nitric oxide. At elevated Ca2+ concentrations, CaM binds to neuronal NOS and endothelial NOS, making them the Ca2+-dependent NOS enzymes. In contrast, inducible NOS is transcriptionally regulated in vivo and binds to CaM at basal levels of Ca2+. Here we report the NMR backbone and sidechain resonance assignments of C-lobe Ca2+-replete and deplete CaM12, N-lobe Ca2+-replete and deplete CaM34, CaM1234 in the absence of Ca2+ and N-lobe Ca2+-replete CaM34 with the iNOS CaM-binding domain peptide.