title: Transition state chirality and role of the vicinal hydroxyl in the ribosomal peptidyl transferase reaction.
abstract: The ribosomal peptidyl transferase is a biologically essential catalyst responsible for protein synthesis. The reaction is expected to proceed through a transition state approaching tetrahedral geometry with a specific chirality. To establish that stereospecificity, we synthesized two diastereomers of a transition state inhibitor with mimics for each of the four ligands around the reactive chiral center. Preferential binding of the inhibitor that mimics a transition state with S chirality establishes the spatial position of the nascent peptide and the oxyanion and places the amine near the critical A76 2'-OH group on the P-site tRNA. Another inhibitor series with 2'-NH 2 and 2'-SH substitutions at the critical 2'-OH group was used to test the neutrality of the 2'-OH group as predicted if the hydroxyl functions as a proton shuttle in the transition state. The lack of significant pH-dependent binding by these inhibitors argues that the 2'-OH group remains neutral in the transition state. Both of these observations are consistent with a proton shuttle mechanism for the peptidyl transferase reaction.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA.
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Huang
authors.forename: Nicolas
authors.initials: N
authors.lastname: Carrasco
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Pfund
authors.forename: Scott A
authors.initials: SA
authors.lastname: Strobel
mesh_terms: D001665:Binding Sites; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D015394:Molecular Structure; D010458:Peptidyl Transferases / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D012343:RNA, Transfer; D010458:Peptidyl Transferases