Interaction of Genome‐linked Protein (VPg) of Turnip Mosaic Virus (TuMV) With Wheat Germ Translation Initiation Factors eIFiso4E and eIFiso4G

The binding between the viral protein linked to the genome (VPg) of turnip mosaic virus (TuMV) and the Wheat germ eukaryotic translation initiation factors eIFiso4E, and eIFiso4G were measured and compared. The fluorescence quenching data showed the presence of one binding site on eIFiso4E for VPg. Scatchard analysis revealed the binding affinity (K a ) and average binding sites (n) for VPg were 25.14 x 10 6 M −1 and 0.85, respectively. Addition of eIFiso4G to the eIFiso4E increases 1.5 times the binding affinity with VPg as compared to the eIFiso4E alone. However, eIFiso4G alone did not bind with VPg. Addition of m 7 G cap to the eIFiso4E‐VPg or eIFiso4E‐iso4G‐VPg complex further increased the binding affinity. The van’t Hoff analyses showed that VPg binding is enthalpy‐driven and entropy favorable with a large negative H° (−28.34 kJmole −1 ), and positive S° (38.40 Jmole −1 K −1 ). These results suggest that the VPg binding site is located on or near the cap recognition pocket on eIFiso4E. Further, the formation of a cap binding complex containing VPg suggests the possibility of direct participation of VPg in the translation of the viral genome. Supported by Research Center in Minority Institution Award RR‐03037 from the National Center for Research Resources of NIH and National Science Foundation Grant MCB 0413982. Grant‐in‐Aid for Scientific Research (16580031) from the Ministry of education, Science, Sports & Culture of Japan.