title: Effect of Src kinase phosphorylation on disordered C-terminal domain of N-methyl-D-aspartic acid (NMDA) receptor subunit GluN2B protein.
abstract: NMDA receptors are ligand-gated ion channels with a regulatory intracellular C-terminal domain (CTD). In GluN2B, the CTD is the largest domain in the protein but is intrinsically disordered. The GluN2B subunit is the major tyrosine-phosphorylated protein in synapses. Src kinase phosphorylates the GluN2B CTD, but it is unknown how this affects channel activity. In disordered proteins, phosphorylation can tip the balance between order and disorder. Transitions can occur in both directions, so it is not currently possible to predict the effects of phosphorylation. We used single molecule fluorescence to characterize the effects of Src phosphorylation on GluN2B. Scanning fluorescent labeling sites throughout the domain showed no positional dependence of the energy transfer. Instead, efficiency only scaled with the separation between labeling sites suggestive of a relatively featureless conformational energy landscape. Src phosphorylation led to a general expansion of the polypeptide, which would result in greater exposure of known protein-binding sites and increase the physical separation between contiguous sites. Phosphorylation makes the CTD more like a random coil leaving open the question of how Src exerts its effects on the NMDA receptor.
authors.affiliation: Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661, USA.
authors.forename: Ucheor B
authors.initials: UB
authors.lastname: Choi
authors.forename: Shifeng
authors.initials: S
authors.lastname: Xiao
authors.forename: Lonnie P
authors.initials: LP
authors.lastname: Wollmuth
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bowen
mesh_terms: D001665:Binding Sites; D006801:Humans; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019061:src-Family Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C121001:NR2B NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D019061:src-Family Kinases