Crampton, Donald J.Guo, ShenyuanJohnson, Donald E.Richardson, Charles C.2019-10-052004Crampton, D. J., S. Guo, D. E. Johnson, and C. C. Richardson. 2004. “The Arginine Finger of Bacteriophage T7 Gene 4 Helicase: Role in Energy Coupling.” Proceedings of the National Academy of Sciences 101 (13): 4373–78. https://doi.org/10.1073/pnas.0400968101.0027-84240744-28311091-6490http://nrs.harvard.edu/urn-3:HUL.InstRepos:41483356The DNA helicase encoded by gene 4 of bacteriophage T7 couples DNA unwinding to the hydrolysis of dTTP. The loss of coupling in the presence of orthovanadate (Vi) suggests that the gamma-phosphate of dTTP plays an important role in this mechanism. The crystal structure of the hexameric helicase shows Arg-522, located at the subunit interface, positioned to interact with the gamma-phosphate of bound nucleoside 5' triphosphate. In this respect, it is analogous to arginine fingers found in other nucleotide-hydrolyzing enzymes. When Arg-522 is replaced with alanine (gp4-R522A) or lysine (gp4-R522K), the rate of dTTP hydrolysis is significantly decreased. dTTPase activity of the altered proteins is not inhibited by Vi, suggesting the loss of an interaction between Vi and gene 4 protein. gp4-R522A cannot unwind DNA, whereas gp4-R522K does so, proportionate to its dTTPase activity. However, gp4-R522K cannot stimulate T7 polymerase activity on double-stranded DNA. These findings support the involvement of the Arg-522 residue in the energy coupling mechanism.en-USJournal Article2019-10-0510.1073/pnas.0400968101