Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10870441 | FEBS Letters | 2015 | 6 Pages |
Abstract
The mutant E270A of Thermus thermophilus 3-isopropylmalate dehydrogenase exhibits largely reduced (â¼1%) catalytic activity and negligible activation by K+ compared to the wild-type enzyme. A 3-4Â kcal/mol increase in the activation energy of the catalysed reaction upon this mutation could also be predicted by QM/MM calculations. In the X-ray structure of the E270A mutant a water molecule was observed to take the place of K+. SAXS and FRET experiments revealed the essential role of E270 in stabilisation of the active domain-closed conformation of the enzyme. In addition, E270 seems to position K+ into close proximity of the nicotinamide ring of NAD+ and the electron-withdrawing effect of K+ may help to polarise the aromatic ring in order to aid the hydride-transfer.
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Authors
Ãva Gráczer, Anna Palló, Julianna Oláh, Tamás Szimler, Petr V. Konarev, Dmitri I. Svergun, Angelo Merli, Péter Závodszky, Manfred S. Weiss, Mária Vas,