title: Gadd45 beta forms a homodimeric complex that binds tightly to MKK7.
abstract: Gadd45 alpha, beta, and gamma proteins, also known as growth arrest and DNA damage-inducible factors, have a number of cellular functions, including cell-cycle regulation and propagation of signals produced by a variety of cellular stimuli, maintaining genomic stability and apoptosis. Furthermore, Gadd45 beta has been indicated as a major player in the endogenous NF-kappaB-mediated resistance to apoptosis in a variety of cell lines. In fibroblasts this mechanism involves the inactivation of MKK7, the upstream activator of JNK, by direct binding within the kinase ATP pocket. On the basis of a number of experimental data, the structures of Gadd45 beta and the Gadd45 beta-MKK7 complex have been predicted recently and data show that interactions are mediated by acidic loops 1 and 2, and helices 3 and 4 of Gadd45 beta. Here, we provide further evidence that Gadd45 beta is a prevailingly alpha-helical protein and that in solution it is able to form non covalent dimers but not higher-order oligomers, in contrast to what has been reported for the homologous Gadd45 alpha. We show that the contact region between the two monomers is comprised of the predicted helix 1 (residues Q17-Q33) and helix 5 (residues K131-R146) of the protein, which appear to be antiparallel and to form a large dimerisation surface not involved in MKK7 recognition. The results suggest the occurrence of a large complex containing at least an MKK7-Gadd45 beta:Gadd45 beta-MKK7 tetrameric unit whose complexity could be further increased by the dimeric nature of the isolated MKK7.
authors.affiliation: Dipartimento delle Scienze Biologiche, Istituto di Biostrutture e Bioimmagini (IBB), CNR, via Mezzocannone, 16, 80134, Napoli, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Tornatore
authors.forename: Daniela
authors.initials: D
authors.lastname: Marasco
authors.forename: Nina
authors.initials: N
authors.lastname: Dathan
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Vitale
authors.forename: Ettore
authors.initials: E
authors.lastname: Benedetti
authors.forename: Salvatore
authors.initials: S
authors.lastname: Papa
authors.forename: Guido
authors.initials: G
authors.lastname: Franzoso
authors.forename: Menotti
authors.initials: M
authors.lastname: Ruvo
authors.forename: Simona Maria
authors.initials: SM
authors.lastname: Monti
mesh_terms: D000595:Amino Acid Sequence; D000943:Antigens, Differentiation / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D002850:Chromatography, Gel; D002942:Circular Dichroism; D019281:Dimerization; D006801:Humans; D048688:MAP Kinase Kinase 7 / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D008969:Molecular Sequence Data; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D000097642:GADD45 Proteins
chemical_list: D000943:Antigens, Differentiation; D048688:MAP Kinase Kinase 7; C086470:GADD45B protein, human; D000097642:GADD45 Proteins; C482569:MAP2K7 protein, human