Interaction between γC87 and γR242 residues participates in energy coupling between catalysis and proton translocation in Escherichia coli ATP synthase.

Functioning as a nanomotor, ATP synthase plays a vital role in the cellular energy metabolism. Interactions at the rotor and stator interface are critical to the energy transmission in ATP synthase. From mutational studies, we found that the γC87K mutation impairs energy coupling between proton translocation and nucleotide synthesis/hydrolysis. An additional glutamine mutation at γR242 (γR242Q) can restore efficient energy coupling to the γC87K mutant. Arrhenius plots and molecular dynamics simulations suggest that an extra hydrogen bond could form between the side chains of γC87K and β TP E381 in the γC87K mutant, thus impeding the free rotation of the rotor complex. In the enzyme with γC87K/γR242Q double mutations, the polar moiety of γR242Q side chain can form a hydrogen bond with γC87K, so that the amine group in the side chain of γC87K will not hydrogen-bond with βE381. As a conclusion, the intra-subunit interaction between positions γC87 and γR242 modulates the energy transmission in ATP synthase. This study should provide more information of residue interactions at the rotor and stator interface in order to further elucidate the energetic mechanism of ATP synthase. • The γC87K mutation impairs energy transmission in E. coli ATP synthase. • Extra hydrogen bond forms between γC87K and the β TP DELSEED loop. • An additional γR242Q/S/C/A mutation can restore the energy transmission. • The γR242E/L mutation cannot restore the energy transmission. • The γR242Q is most effective to suppress the energy uncoupling. [ABSTRACT FROM AUTHOR]