ИСТИНА

The ATPase activity of H+-FoF1-ATP synthase can be regulated in several ways, the most common of which is MgADP-dependent inhibition. When proton electrochemical gradient across the membrane is low, MgADP binding to the catalytic site in the absence of phosphate may lead to ATP synthase inactivation. The degree of this inhibition varies greatly between different organisms: ATP synthase in chloroplast, mitochondria and some bacteria (Bacillus PS3, Bacillus subtilis) has strong MgADP-inhibition, whereas it is much weaker in Escherichia coli enzyme. Also, it was shown that phosphate addition activates Bacillus PS3 ATP-synthase but inhibits ATP-synthase in Escherichia coli. The ATP synthase beta subunit sequences from Escherichia coli and Bacillus PS3 are quite similar, however there are a few substitutions including positions 189 (phenylalanine in E. coli and leucin in B. PS3) and 249 (leucin in E. coli and glutamine in Bacillus PS3). We have previously shown that point mutations F189L and L249Q in beta subunit of Escherichia coli ATP synthase both changed the effect of phosphate on ATPase activity and βL249Q mutation enhanced MgADP-dependent inhibition. In this work, we report that double mutation βL249Q+F189L leads to phosphate effect alteration and even stronger MgADP-dependent inhibition enhancement than the single mutation βL249Q.