Conformational dynamics monitored by His‐179 and His‐200 of isolated thermophilic F1‐ATPase β subunit which reside at the entrance of the ‘conical tunnel’ in holoenzyme

Abstract
When monitored by 1H NMR at various pH values, most of the C‐2 proton signals from 12 His residues of the isolated β subunit of thermophilic F1‐ATPase (TF1) could be separately observed. Two of them were assigned to His‐179 and His‐200 which reside at the entrance of a ‘conial tunnel’ to reach catalytic site in the crystal structure of F1‐ATPase. His‐200 gave doublet, suggesting that this region is not a rigid α‐helix in the isolated β subunit. The binding of Mg · AMP‐PNP changed the chemical shifts of His‐179 and His‐200 significantly. Although His‐119 located at the opposite side of the conical tunnel was not affected by the nucleotide‐binding, it contributed to the stability of β subunit and the efficiency of the catalysis of the holoenzyme.