title: Thermodynamic analysis reveals that GTP binding affects the interaction between the alpha- and gamma-subunits of translation initiation factor 2.
abstract: Eukaryotic and archaeal translation initiation factors 2, heterotrimers that consist of alpha-, beta-, and gamma-subunits, deliver methionylated initiator tRNA to a small ribosomal subunit in a manner that depends on GTP. To evaluate correlation of the function and association of the subunits, we used isothermal titration calorimetry to analyze the thermodynamics of the interactions between the alpha- and gamma-subunits in the presence or absence of a nonhydrolyzable GTP analog or GDP. The alpha-subunits bound to the gamma-subunit with large heat capacity change (DeltaC(p)) values. The DeltaH and DeltaC(p) values for the interaction between the alpha- and gamma-subunits varied in the presence of the GTP analog but not in the presence of GDP. These results suggest that the binding of both the alpha-subunit and GTP changes the conformation of the switch region of the gamma-subunit and increases the affinity of the gamma-subunit for tRNA.
authors.affiliation: Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 301 FBS-Building, 5-1-5 Kashiwanoha, Kashiwa 277-8562, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakakido
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Masaaki
authors.initials: M
authors.lastname: Sokabe
authors.forename: Kouhei
authors.initials: K
authors.lastname: Tsumoto
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics; D003461:Crystallography; D004926:Escherichia coli / Q000235:genetics; D006153:Guanosine Diphosphate / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry*; D039881:Prokaryotic Initiation Factor-2 / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics; D048229:Sulfolobus solfataricus; D013816:Thermodynamics
chemical_list: D019843:Archaeal Proteins; C503923:GDPNP compound; D039881:Prokaryotic Initiation Factor-2; D021122:Protein Subunits; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate