title: A highly conserved cysteine of neuronal calcium-sensing proteins controls cooperative binding of Ca2+ to recoverin.
abstract: Recoverin, a 23-kDa Ca(2+)-binding protein of the neuronal calcium sensing (NCS) family, inhibits rhodopsin kinase, a Ser/Thr kinase responsible for termination of photoactivated rhodopsin in rod photoreceptor cells. Recoverin has two functional EF hands and a myristoylated N terminus. The myristoyl chain imparts cooperativity to the Ca(2+)-binding sites through an allosteric mechanism involving a conformational equilibrium between R and T states of the protein. Ca(2+) binds preferentially to the R state; the myristoyl chain binds preferentially to the T state. In the absence of myristoylation, the R state predominates, and consequently, binding of Ca(2+) to the non-myristoylated protein is not cooperative. We show here that a mutation, C39A, of a highly conserved Cys residue among NCS proteins, increases the apparent cooperativity for binding of Ca(2+) to non-myristoylated recoverin. The binding data can be explained by an effect on the T/R equilibrium to favor the T state without affecting the intrinsic binding constants for the two Ca(2+) sites.
authors.affiliation: From the Department of Biochemistry and.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Ranaghan
authors.forename: Ramasamy P
authors.initials: RP
authors.lastname: Kumar
authors.forename: Kalyan S
authors.initials: KS
authors.lastname: Chakrabarti
authors.forename: Vanessa
authors.initials: V
authors.lastname: Buosi
authors.forename: Dorothee
authors.initials: D
authors.lastname: Kern
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Oprian
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D017124:Conserved Sequence; D003545:Cysteine; D008958:Models, Molecular; D016296:Mutagenesis; D009154:Mutation; D010084:Oxidation-Reduction; D011485:Protein Binding; D051603:Recoverin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D051603:Recoverin; D003545:Cysteine; D002118:Calcium
keywords: Allosteric Regulation; Calcium Signaling; Calcium-binding Proteins; Cooperativity; Cysteine; Mutant; Neuronal Calcium Sensor; Protein Myristoylation; Sulfenic Acid