The catalytic transition state in ATP synthase.
The catalytic transition state of ATP synthase has been characterized and modeled by combined use of (1) Mg-ADP-fluoroaluminate, Mg-ADP-fluoroscandium, and corresponding Mg-IDP-fluorometals as transition-state analogs; (2) fluorescence signals of beta-Trp331 and beta-Trp148 as optical probes to assess formation of the transition state; (3) mutations of critical catalytic residues to determine side-chain ligands required to stabilize the transition state. Rate acceleration by positive catalytic site cooperativity is explained as due to mobility of alpha-Arg376, acting as an "arginine finger" residue, which interacts with nucleotide specifically at the transition state step of catalysis, not with Mg-ATP- or Mg-ADP-bound ground states. We speculate that formation and collapse of the transition state may engender catalytic site alpha/beta subunit-interface conformational movement, which is linked to gamma-subunit rotation.
Senior
A E
AE
Department of Biochemistry and Biophysics, Box 712, University of Rochester Medical Center, Rochester, New York 14642, USA. alan_senior@urmc.rochester.edu
Weber
J
J
Nadanaciva
S
S
D000818:Animals; D020134:Catalytic Domain / Q000235:genetics; D005456:Fluorescent Dyes; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D021122:Protein Subunits; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000737:chemistry
D005456:Fluorescent Dyes; D021122:Protein Subunits; D014364:Tryptophan; D006180:Proton-Translocating ATPases