title: A new calmodulin-binding motif for inositol 1,4,5-trisphosphate 3-kinase regulation.
abstract: IP3-3K [Ins(1,4,5)P3 3-kinase] is a key enzyme that catalyses the synthesis of Ins(1,3,4,5)P4, using Ins(1,4,5)P3 and ATP as substrates. Both inositides, substrate and product, present crucial roles in the cell. Ins(1,4,5)P3 is a key point in Ca2+ metabolism that promotes Ca2+ release from intracellular stores and together with Ins(1,3,4,5)P4 regulates Ca2+ homoeostasis. In addition, Ins(1,3,4,5)P4 is involved in immune cell development. It has been proved that Ca2+/CaM (calmodulin) regulates the activity of IP3-3K, via direct interaction between both enzymes. Although we have extensive structural knowledge of the kinase domains of the three IP3-3K isoforms, no structural information is available about the interaction between IP3-3K and Ca2+/CaM. In the present paper we describe the crystal structure of the complex between human Ca2+/CaM and the CaM-binding region of human IP3-3K isoform A (residues 158-183) and propose a model for a complex including the kinase domain. The structure obtained allowed us to identify all of the key residues involved in the interaction, which have been evaluated by site-directed mutagenesis, pull-down and fluorescence anisotropy experiments. The results allowed the identification of a new CaM-binding motif, expanding our knowledge about how CaM interacts with its partners.
authors.affiliation: *Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: Elsa
authors.initials: E
authors.lastname: Franco-Echevarría
authors.affiliation: *Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: Jose I
authors.initials: JI
authors.lastname: Baños-Sanz
authors.affiliation: †Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain.
authors.forename: Begoña
authors.initials: B
authors.lastname: Monterroso
authors.affiliation: ‡European Molecular Biology Laboratory, Grenoble Outstation, 6 Rue Jules Horowitz, 38042 Grenoble, France.
authors.forename: Adam
authors.initials: A
authors.lastname: Round
authors.affiliation: *Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: Julia
authors.initials: J
authors.lastname: Sanz-Aparicio
authors.affiliation: *Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: González
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D002147:Calmodulin / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry; D009154:Mutation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D002147:Calmodulin; D007527:Isoenzymes; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase