The Stator Subunits of the ATP Synthase

Southern Methodist University, Dallas TX

Investigators

Abstract

The FoF1-ATP synthase catalyzes the synthesis of the universal energy carrier, ATP, by using the energy of a proton gradient across energy coupling membranes. Nature's elegant design to solve the problem of energy transduction has intrigued researchers over the last decades. The finding that rotation of some of the subunits of FoF1 are part of the catalytic mechanism has brought the attention of investigators also to the structure and function of those subunits that most likely do not participate in rotation, especially the stator subunits beta. Special focus has been placed on the structure of the beta-dimer because it may be a means to store and deliver elastic energy during rotational catalysis. There are three main goals to this project: (1) The dimer interactions and helical packing of the subunit beta dimer will be studied in a truncated, water soluble version of beta to determine the quaternary structure of this second stalk of the ATP-synthase. Site-specific spin labeling and ESR-spectroscopy will be used to determine inter-spin and inter-helix distances. This will allow the construction of a model for the structure of the beta - dimer. (2) The use of beta subunits that contain double mutations within one beta monomer will shed light on potential tertiary structures of beta and will solve the question concerning the overall length of the beta subunit compared to the F1-structure. To reach this goal, spin-labels will be introduced at defined positions along a single beta -chain. The distances of the spins as determined by dipolar spin interactions will provide information about the tertiary structure of beta. (3) It is hypothesized that the structure of the beta - dimer may change upon interaction with F1 or in the complete FoF1-complex due to changed protein interaction surfaces. Introduction of the mutants from project 1 into a cys-less FoF1-background will allow studies of potential differences in the tertiary and quaternary structure of the beta - dimer in the complete, detergent-solubilized FoF1-complex. The data in all projects will be refined using high-field ESR techniques. The proposed investigations are organized to involve undergraduate and graduate students. Small projects will be made available also to interested high school students. Both teaching and learning experiences will be important for the development of a new generation of scientists. The students joining this laboratory will therefore be able to get first hand experience with state of the art techniques in biophysics. A molecular modeling course using the available Silicon Graphics hardware and modeling software will be developed for students at the graduate level.