GTP hydrolysis by IF2 guides progression of the ribosome into elongation.
Recent structural data have revealed two distinct conformations of the ribosome during initiation. We employed single-molecule fluorescence methods to probe the dynamic relation of these ribosomal conformations in real time. In the absence of initiation factors, the ribosome assembles in two distinct conformations. The initiation factors guide progression of the ribosome to the conformation that can enter the elongation cycle. In particular, IF2 both accelerates the rate of subunit joining and actively promotes the transition to the elongation-competent conformation. Blocking GTP hydrolysis by IF2 results in 70S complexes formed in the conformation unable to enter elongation. We observe that rapid GTP hydrolysis by IF2 drives the transition to the elongation-competent conformation, thus committing the ribosome to enter the elongation cycle.
Marshall
R Andrew
RA
Department of Chemistry, Stanford University, Stanford, CA 94305-5126, USA.
Aitken
Colin Echeverría
CE
Puglisi
Joseph D
JD
D002232:Carbocyanines / Q000737:chemistry; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D006160:Guanosine Triphosphate / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000378:metabolism*; D039881:Prokaryotic Initiation Factor-2 / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism*
D002232:Carbocyanines; D015852:Eukaryotic Initiation Factor-2; D010448:Peptide Initiation Factors; D039881:Prokaryotic Initiation Factor-2; D012333:RNA, Messenger; C089187:cyanine dye 3; C085321:cyanine dye 5; D006160:Guanosine Triphosphate; D012343:RNA, Transfer