The photosynthetic ATP synthase of higher plants is a tiny molecular rotary motor with several unique properties that separate it from its mitochondrial and bacterial counterparts and offer unique inroads to examine the mechanism of energy coupling. One such property is the presence of a special regulatory domain within the gamma subunit which, via the reversible oxidation/reduction of an intrinsic dithiol, governs an interaction with the inhibitory epsilon subunit. This interaction provides a molecular switch mechanism that tightly controls the catalytic activity of the enzyme, preventing futile hydrolysis of ATP in the absence of a membrane potential. The objective of this project is to identify the productive binding interactions between the gamma and epsilon subunits, and between these two subunits and the other F1 subunits, that are involved in the molecular switch mechanism. Specific aims are: 1) To determine the inter-subunit conformational interplay that results in CF1 activation and proton coupling using dithiol cross-linking and dynamic single molecule fluorescence approaches; and 2) To determine the three-dimensional structures of the epsilon, delta and gamma subunits using solution NMR and x-ray crystallographic approaches.
The intellectual merit of the project stems from the fact that the ATP synthase plays a central role in energy capture and inter-conversion in living systems. The results from this work is likely to provide an understanding of natural processes that have evolved to gate the motor, in identifying the mechanism of elastic coupling between the FO and F1 segments, and in designing gated nanodevices for future industrial applications. This project will have a number of broader impacts including training of undergraduate and graduate students and postdoctoral associates in emerging areas of nanotechnology including advanced molecular engineering and analysis methods. The research will dovetail with a newly established, NSF-funded, multidisciplinary and interdisciplinary undergraduate training program in nanoscience and will be integrated with ongoing diversity and outreach programs on the university campus and within the state of Kansas.
