PMID:21383131
| Citation |
Beke-Somfai, T, Lincoln, P and Nordén, B (2011) Double-lock ratchet mechanism revealing the role of alphaSER-344 in FoF1 ATP synthase. Proc. Natl. Acad. Sci. U.S.A. 108:4828-33 |
|---|---|
| Abstract |
In a majority of living organisms, FoF1 ATP synthase performs the fundamental process of ATP synthesis. Despite the simple net reaction formula, ADP+Pi→ATP+H2O, the detailed step-by-step mechanism of the reaction yet remains to be resolved owing to the complexity of this multisubunit enzyme. Based on quantum mechanical computations using recent high resolution X-ray structures, we propose that during ATP synthesis the enzyme first prepares the inorganic phosphate for the γP-OADP bond-forming step via a double-proton transfer. At this step, the highly conserved αS344 side chain plays a catalytic role. The reaction thereafter progresses through another transition state (TS) having a planar ion configuration to finally form ATP. These two TSs are concluded crucial for ATP synthesis. Using stepwise scans and several models of the nucleotide-bound active site, some of the most important conformational changes were traced toward direction of synthesis. Interestingly, as the active site geometry progresses toward the ATP-favoring tight binding site, at both of these TSs, a dramatic increase in barrier heights is observed for the reverse direction, i.e., hydrolysis of ATP. This change could indicate a "ratchet" mechanism for the enzyme to ensure efficacy of ATP synthesis by shifting residue conformation and thus locking access to the crucial TSs. |
| Links |
PubMed PMC3064393 Online version:10.1073/pnas.1010453108 |
| Keywords |
Adenosine Triphosphate/biosynthesis; Adenosine Triphosphate/chemistry; Catalysis; Escherichia coli/enzymology; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/metabolism; Models, Molecular; Proton-Translocating ATPases/chemistry; Proton-Translocating ATPases/metabolism; Serine/chemistry; Serine/metabolism |
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