Characterizing the Role of the Epsilon Subunit in Regulation of the Escherichia coli ATP Synthase.

Abstract

The F-type ATP synthase is a rotary nanomotor central to cellular energy metabolism in almost all living organisms. In bacteria, the enzyme also plays a role in nutrient uptake and pH regulation underlining its importance. All ATP synthases can be inhibited by ADP, whereas in bacteria, the enzyme is alsoautoinhibitedbyits ε subunit. The inhibition involves a drastic conformationa l change of the C-terminal domain of the ε subunit (εCTD)thatblockscatalytic turnover. Thisregulation by ε is believed to play an important role in maintaining viability of the cell. Recent development in the field of antibiotics has validated ATP synthase as a drug target against pathogenic bacteria. Thus, there is a renewed interest in studying the role of the ε subunit in regulation of the enzyme and exploiting it to develop antimicrobials that can kill pathogenic bacteria. The present work describes advances in our understanding of the regulatory interactions of εCTD in E. coli ATP synthase.In the first approach, we used an optical binding assay to understand the transitions of εCTD between its active and inhibitory conformations.Using different ligands we revealedthe relationship between ADP inhibition and ε inhibition. In the second novel approach, the terminal five amino acids of εCTD were deleted to observe the effects on in vivo and in vitro functions of ATP synthase. The results obtained from these studies advance our understanding of εinhibition inbacteria and also provide a noveltarget within bacterial ATP synthase to obtain antibacterial drugs.