title: Interdomain interactions regulate the activation of the heme-regulated eIF 2 alpha kinase.
abstract: The heme-regulated inhibitor of protein synthesis (HRI) regulates translation through the phosphorylation of the alpha-subunit of eukaryotic initiation factor-2 (eIF 2). While HRI is best known for its activation in response to heme-deficiency, we recently showed that the binding of NO and CO to the N-terminal heme-binding domain (NT-HBD) of HRI activated and suppressed its activity, respectively. Here, we examined the effect of hemin, NO, and CO on the interaction between the NT-HBD and the catalytic domain of HRI (HRI/Delta HBD). Hemin stabilized the interaction of NT-HBD with HRI/Delta HBD, and NO and CO disrupted and stabilized this interaction, respectively. Mutant HRI (Delta H-HRI), lacking amino acids 116-158 from the NT-HBD, was less sensitive to heme-induced inhibition, and mutant NT-HBD lacking these residues did not bind to HRI/Delta HBD. HRI/Delta HBD and Delta H-HRI also activated more readily than HRI in response to heme-deficiency. Thus, HRI's activity is regulated through the modulation of the interaction between its NT-HBD and catalytic domain.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, 246 NRC, Stillwater, OK 74078-3035, USA.
authors.forename: Bo-Geon
authors.initials: BG
authors.lastname: Yun
authors.forename: Jessica A B
authors.initials: JA
authors.lastname: Matts
authors.forename: Robert L
authors.initials: RL
authors.lastname: Matts
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry*; D002478:Cells, Cultured; D004789:Enzyme Activation; D006418:Heme / Q000737:chemistry*; D016297:Mutagenesis, Site-Directed; D009569:Nitric Oxide / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011994:Recombinant Proteins / Q000032:analysis / Q000737:chemistry; D012156:Reticulocytes / Q000201:enzymology*; D013329:Structure-Activity Relationship; D019892:eIF-2 Kinase / Q000032:analysis* / Q000737:chemistry* / Q000235:genetics
chemical_list: D011994:Recombinant Proteins; D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide; D019892:eIF-2 Kinase