Pi release from eIF2, not GTP hydrolysis, is the step controlled by start-site selection during eukaryotic translation initiation.
Irreversible GTP hydrolysis by eIF2 is a critical step in translation initiation in eukaryotes because it is thought to commit the translational machinery to assembling the ribosomal complex at the selected point in the mRNA. Our quantitative analysis of the steps and interactions involved in activating GTP hydrolysis by eIF2 during translation initiation in vitro indicates that a structural rearrangement in the 43S preinitiation complex activates it to become fully competent to hydrolyze GTP. Contrary to the prevailing model, release of inorganic phosphate after GTP hydrolysis by eIF2, not hydrolysis itself, is controlled by recognition of the AUG codon. Release of P(i), which makes GTP hydrolysis irreversible, appears to be controlled by the AUG-dependent dissociation of eIF1 from the preinitiation complex.
Algire
Mikkel A
MA
Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Maag
David
D
Lorsch
Jon R
JR
D018387:Codon, Initiator / Q000235:genetics* / Q000378:metabolism; D005057:Eukaryotic Cells / Q000737:chemistry / Q000378:metabolism; D015977:Eukaryotic Initiation Factor-1 / Q000235:genetics / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D040061:Eukaryotic Initiation Factor-5 / Q000235:genetics / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012335:RNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics; D013997:Time Factors
D018387:Codon, Initiator; D015977:Eukaryotic Initiation Factor-1; D015852:Eukaryotic Initiation Factor-2; D040061:Eukaryotic Initiation Factor-5; D010710:Phosphates; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D006160:Guanosine Triphosphate