F1F0 ATP synthases

Proton translocation down an electrochemical gradient across the energy transducing membranes drives the synthesis of ATP by F1F0 ATP synthase. The F1F0 ATP synthases from all species share a common molecular architecture that extends down to the level of primary sequence homology. These are very large enzymes of approximately 500 kDa composed of more than 20 proteins of at least eight different types. The molecular mechanism involves a fascinating rotational motion within the enzyme that has recently been popularized as the world's smallest rotary motor. In humans, changes in energy metabolism are associated with many disease states ranging from cancer to aging. Mutations in ATP synthase subunits are directly associated with a group of devastating inheritable diseases termed the mitochondrial myopathies.

We are particularly interested in proton translocation and the coupling of proton translocation to ATP synthesis. Our studies focus specifically on the a and b subunits of the F0 sector of the Escherichia coli F1F0 ATP synthase. Both subunits are embedded in the membrane. Our laboratory was instrumental in demonstrating that the proton channel through F0 is located in the a subunit, and we have made important contributions to understanding the role of the b subunit in the peripheral stalk structure that links the F1 and F0 sectors. We are continuing to pursue questions about the functional roles of both subunits and the assembly of this complicated enzyme complex. The primary methods for these studies include extensive use of site-directed mutagenesis, protein purification, chemical cross-linking and a variety of catalytic activity measurements. The laboratory has enjoyed continuous funding for this project from the National Institutes of Health for more than a decade.

Recent Publications

Gardner, J.L. and Cain, B.D. (2000) The a subunit ala-217 -> arg substitution affects catalytic activity of F1F0 ATP synthase. Archives of Biochemistry and Biophysics 380(1): 201-207.

Cain, B.D. (2000) Mutagenic analysis of the F0 stator subunits. Journal of Bioenergetics and Biomembranes 32(4): 365-371.

Sorgen, P.L., Bubb, M.R., and Cain, B.D. (1999) Lengthening the second stalk of F1F0 ATP synthase in Escherichia coli. Journal of Biological Chemistry 274(51): 36261-36266.

Hartzog, P.E., Gardner, J.L., and Cain, B.D. (1999) Modeling the Leigh syndrome nt8993 T -> C mutation in Escherichia coli F1F0 ATP synthase. The International Journal of Biochemistry & Cell Biology 31: 769-776.

Gardner, J.L. and Cain, B.D. (1999) Amino acid substitutions in the a subunit affect the e subunit of F1F0 ATP synthase from Escherichia coli. Archives of Biochemistry and Biophysics 361(2): 302-308

Sorgen, P.L., Caviston, T.L., Perry, R.C., and Cain, B.D. (1998) Deletions in the second stalk of F1F0 -ATP synthase in Escherichia coli. Journal of Biological Chemistry 273 (43): 27873-27878.

Sorgen, P.L., Bubb, M.R., McCormick, K.A., Edison, A.S., and Cain, B.D. (1998) Formation of the b subunit dimer is necessary for the interaction with F1-ATPase. Biochemistry 37(3): 923-932.

Caviston, T.L., Ketchum, C.J., Sorgen, P.L., Nakamoto, R.K., and Cain, B.D. (1998) Identification of an uncoupling mutation affecting the b subunit of F1F0 ATP synthase in Escherichia coli. FEBS Letters 429: 201-206.