Tautomeric stabilities of 4-fluorohistidine shed new light on mechanistic experiments with labeled ribonuclease A
Ellis, Jonathan M.
Bann, James G.
Mitchell-Koch, Katie R.
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Kasireddy, Chandana; Ellis, Jonathan M.; Bann, James G.; Mitchell-Koch, Katie R. 2016. Tautomeric stabilities of 4-fluorohistidine shed new light on mechanistic experiments with labeled ribonuclease A. Chemical Physics Letters, vol. 666:pp 58–61
Ribonuclease A is the oldest model for studying enzymatic mechanisms, yet questions remain about proton transfer within the active site. Seminal work by Jackson et al. (1994) labeled Ribonuclease A with 4-fluorohistidine, concluding that active-site histidines act as general acids and bases. Calculations of 4-fluorohistidine indicate that the pi-tautomer is predominant in all simulated environments (by similar to 17 kJ/mol), strongly suggesting that fluoro-labeled ribonuclease A functions with His119 in pi-tautomer. The tautomeric form of His119 during proton transfer and tautomerism as a putative mechanistic step in wild-type RNase A remain open questions and should be considered in future mechanistic studies.
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