title: Activation of GTP hydrolysis in mRNA-tRNA translocation by elongation factor G.
abstract: During protein synthesis, elongation of the polypeptide chain by each amino acid is followed by a translocation step in which mRNA and transfer RNA (tRNA) are advanced by one codon. This crucial step is catalyzed by elongation factor G (EF-G), a guanosine triphosphatase (GTPase), and accompanied by a rotation between the two ribosomal subunits. A mutant of EF-G, H91A, renders the factor impaired in guanosine triphosphate (GTP) hydrolysis and thereby stabilizes it on the ribosome. We use cryogenic electron microscopy (cryo-EM) at near-atomic resolution to investigate two complexes formed by EF-G H91A in its GTP state with the ribosome, distinguished by the presence or absence of the intersubunit rotation. Comparison of these two structures argues in favor of a direct role of the conserved histidine in the switch II loop of EF-G in GTPase activation, and explains why GTP hydrolysis cannot proceed with EF-G bound to the unrotated form of the ribosome.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, 2-221 Blackwell, 165 West 168th Street, New York, NY 10032, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, 2-221 Blackwell, 165 West 168th Street, New York, NY 10032, USA.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124 Uppsala, Sweden.
authors.forename: Ravi Kiran
authors.initials: RK
authors.lastname: Koripella
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, 2-221 Blackwell, 165 West 168th Street, New York, NY 10032, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Langlois
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC, 75124 Uppsala, Sweden.
authors.forename: Suparna
authors.initials: S
authors.lastname: Sanyal
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, 2-221 Blackwell, 165 West 168th Street, New York, NY 10032, USA ; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA ; Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
authors.forename: Joachim
authors.initials: J
authors.lastname: Frank