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FEBS Lett. 1996 Nov 11;397(1):122-6.

Unusual pKa of the carboxylate at the putative catalytic position of the thermophilic F1-ATPase beta subunit determined by 13C-NMR.

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Department of Bioengineering, Faculty of Engineering, Yokohama National University, Japan.


Glutamic acid-190 in the beta subunit of F1-ATPase from thermophilic Bacillus PS-3 (TF1) was reported to be essential for the ATPase activity. The mutant TF1beta subunit in which Glu-190 had been substituted by cysteine was carboxymethylated with 13C-labeled monoiodoacetic acid. The pKa value of the carboxymethylene group at the 190 position was determined as 5.6 +/- 0.4 by 13C-NMR. On the basis of this value, the pKa of the carboxylate of Glu-190 of the TF1beta subunit was estimated to be 6.8 +/- 0.5. The unusually high pKa could play a role in the catalytic mechanism of F1-ATPase.

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