Thermodynamic analysis reveals that GTP binding affects the interaction between the alpha- and gamma-subunits of translation initiation factor 2 |
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Authors: | Nakakido Makoto Tanaka Yoshikazu Sokabe Masaaki Tsumoto Kouhei |
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Institution: | a 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 b Faculty of Advanced Life Sciences, Hokkaido University, Sapporo 060-0810, Japan |
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Abstract: | Eukaryotic and archaeal translation initiation factors 2, heterotrimers that consist of α-, β-, and γ-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 α- and γ-subunits in the presence or absence of a nonhydrolyzable GTP analog or GDP. The α-subunits bound to the γ-subunit with large heat capacity change (ΔCp) values. The ΔH and ΔCp values for the interaction between the α- and γ-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 α-subunit and GTP changes the conformation of the switch region of the γ-subunit and increases the affinity of the γ-subunit for tRNA. |
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Keywords: | Met-tRNAi methionylated initiator tRNA eIF eukaryotic translation initiation factor aIF archaeal translation initiation factor GDPNP guanosine 5&prime -[β γ-imido]triphosphate ITC isothermal titration calorimetry SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis |
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