title: Intersubunit and interprotein interactions of alpha- and beta-subunits of human eIF2: Effect of phosphorylation.
abstract: Purified recombinant human subunits of eukaryotic initiation factor 2 (eIF2) expressed in bacteria are found to interact with each other to form alphabeta, alphagamma, and betagamma complexes in a pull-down experiment. Recombinant phosphorylated human eIF2alpha that cannot interact with purified eIF2B, the GDP/GTP exchange factor of eIF2, however interacts efficiently with eIF2B along with the beta-subunit of eIF2 of the rabbit reticulocyte lysates and also with the purified recombinant beta-subunit. These findings therefore suggest that the beta-subunit of eIF2 mediates the productive and non-productive interactions between eIF2 and 2B. Recombinant alpha and beta-subunits serve as substrates for not only kinases but also for caspase 3 and interestingly phosphorylated subunits resist caspase action. Phosphorylation also modifies the beta-subunit's interaction with Nck1, a cofactor of eIF2alpha phosphatase, but not with eIF5, the GTPase activating protein. These findings suggest that subunits of mammalian eIF2 interact with each other and the beta-subunit plays a critical role both in the regulation and function of eIF2.
authors.affiliation: Department of Biochemistry, University of Hyderabad, Gachibowli, Hyderabad 500 046, Andhra Pradesh, India.
authors.forename: Kamindla
authors.initials: K
authors.lastname: Rajesh
authors.forename: Aarti
authors.initials: A
authors.lastname: Iyer
authors.forename: Rajasekhar N V S
authors.initials: RN
authors.lastname: Suragani
authors.forename: Kolluru V A
authors.initials: KV
authors.lastname: Ramaiah
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D004926:Escherichia coli / Q000235:genetics; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D015513:Oncogene Proteins / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism; D010766:Phosphorylation; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D000097574:Eukaryotic Translation Initiation Factor 5A
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015852:Eukaryotic Initiation Factor-2; D015513:Oncogene Proteins; D010448:Peptide Initiation Factors; D021122:Protein Subunits; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D000097574:Eukaryotic Translation Initiation Factor 5A; C078332:Nck protein