Sensing Protein Surfaces with Targeted Fluorescent Receptors

A methodology for creating fluorescent molecular sensors that respond to changes that occur on the surfaces of specific proteins is presented. This approach, which relies on binding cooperatively between a specific His-tag binder and a nonspecific protein-surface receptor, enabled the development of a sensor that can track changes on the surface of a His-tag-labeled calmodulin (His-CaM) upon interacting with metal ions, small molecules, and protein binding partners. The way this approach was used to detect dephosphorylation of an unlabeled calmodulin-dependent protein kinase II (CaMKII), and the binding of Bax BH3 to His-tagged B-cell lymphoma 2 (Bcl-2) protein is also presented.