Response to Comment on "The Mechanism for Activation of GTP Hydrolysis on the Ribosome"

Our report of the crystal structure of elongation factor Tu (EF-Tu) and aminoacyl–transfer RNA bound to the ribosome with a guanosine triphosphate (GTP) analog included a proposed mechanism of GTP hydrolysis by EF-Tu involving histidine-84. Liljas et al. summarize experimental evidence against this mechanism and propose a substrate-assisted catalytic model. However, these experiments and the model are also problematic. Further study is required to definitively determine the mechanism of GTP hydrolysis by EF-Tu