a-crofts@life.uiuc.edu
153 Davenport Hall
Office: (217) 333-2043
Lab: (217) 333-7407
Fax: (217) 244-6615
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Department of Biochemistry
419 Roger Adams Lab B-4
600 S Mathews Ave
Urbana, IL 61801
Antony R Crofts
Professor of Biochemistry
Professor of Biophysics and Computational Biology
Affiliate, Beckman Institute
Education
B.A. 1961 University of Cambridge, U.K.
Ph.D. 1965 University of Cambridge, U.K.
Postdoc. 1965-66, Dept. of Physiology, U.C., Berkeley
Teaching Interests
Structure/function relationships in photosynthetic energy conversion; structure of membrane proteins; mechanism of energy conservation; photosynthesis in intact plants; energetics of the biosphere
Our work is based on the complementarities between biophysical, structural and molecular engineering approaches to the study of biological mechanism. The utility of molecular engineering for modification of protein structure is greatly increased by combining this with other approaches. Most importantly, knowledge of the structure of the target protein from crystallography and spectroscopy and the ability to assay the functional consequences of specific mutagenesis make it possible to explore the mechanism of catalysis at the molecular level.
Ubiquinol:cytochrome c2 oxidoreductase (bc1 complex) of Rb. sphaeroides. With crystallographic structures now available, we are able to take advantage of spectroscopic techniques and protocols for protein engineering that allow us to modify the three catalytic subunits, and ask specific questions about the structure, function and topology of the complex. Our studies have revealed novel mechanisms of electron transfer in the bc1 complex; one involves a dramatic domain movement of the extrinsic domain of the iron sulfur protein; more tentative is another proposal for movement of a semiquinone intermediate at the catalytic site. Detailed spectroscopic studies (ESEEM, ENDOR, resonance Raman) allow us to probe structure local to catalytic intermediates that are not accessible through crystallography. We are currently studying these using a variety of biophysical, biochemical and molecular engineering approaches, including several local and international collaborative projects.
In photosystem II, our present work centers on the function and structure of the two-electron gate through which the photosystem reduces the plastoquinone pool, and on the mechanism of oxygen evolution. Structures now available confirm the conformation we predicted for the QB-site of photosystem II, and therefore lend support to the conclusions drawn from biophysical assays for the reactions, and mutagenesis using PCR-based in Chlamydomonas.
Other interests include biophysical aspects of electron transfer and the coupling to ATP synthesis through the proton gradient; studies of the control of photosynthetic electron transfer in the coupled steady-state; the supramolecular organization of electron transfer chains; the mechanism and evolution of the cyt bc1/b6f family of complexes in plants and bacteria; and the mechanism of action of inhibitors (including herbicides). We have developed novel instruments that allow us to explore individual reactions of the photosynthetic apparatus in intact plants. We are using these in the lab and in the field to try to understand how photosynthesis is regulated under natural conditions, including studies of the mechanisms of down regulation in strong light, photo-inhibition, and response to environmental stress, including insect herbivory. Attempts to quantify global energy fluxes in the biosphere introduce questions about the role of information content, leading to more philosophical interests.
Representative Publications
Crofts, A.R. 2004. The cytochrome bc1 complex - Function in the context of structure. Annu. Rev. Physiol., 66:689–733.
Crofts, A.R. 2004. The Q-cycle - a personal perspective. Photosynth. Res., 80:223–43.
Petrouleas, V. and Crofts, A.R. 2004. The functional organization of the quinone binding sites in photosystem II, in: Photosystem II: The water/plastoquinone oxido-reductase in photosynthesis (Wydrzynski, T. and Satoh, K., eds.). Kluwer Academic Publications, in press.
Iwasaki, T., Kounosu, A., Kolling, D.R.J., Crofts, A.R., Dikanov, S.A., Jin, A., Imai, T., and Urushiyama, A. 2004. Characterization of the pH-dependent resonance raman transitions of archaeal and bacterial ieske [2Fe-2S] proteins. J. Am. Chem. Soc., 126:4788–9.
Dikanov, S.A., Samoilova, R.I., Kolling, D.R.J., Holland, J.T., and Crofts, A.R. 2004. Hydrogen bonds involved in binding the Qi-site semiquinone in the bc1 complex, identified through deuterium exchange using pulsed EPR. J. Biol. Chem., 279;15814–23.
Crofts, A.R. 2004. Proton-coupled electron transfer at the Qo-site of the bc1 complex controls the rate of ubihydroquinone oxidation. Biochim. Biophys. Acta, 1655:77–92.
Zu, Y., Manon, M.J., Couture, M.M.J., Kolling, D.R.J., Crofts, A.R., Eltis, L.D., Fee, J.A., and Hirst, J. 2003. The reduction potentials of rieske clusters: the importance of the coupling between oxidation state and histidine protonation state. Biochemistry, 42:12400–8.
Kolling, D.R.J., Samoilova, R.I., Holland, J.T., Berry, E.A, Dikanov, S.A., and Crofts, A.R. 2003. Exploration of ligands to the Qi-site semiquinone in the bc1 complex using high resolution EPR. J. Biol. Chem., 278:39747–54.
Crofts, A.R., Shinkarev, V.P., Kolling, D.R.J., and Hong, S. 2003. The modified Q-cycle explains the apparent mismatch between the kinetics of reduction of cytochromes c1 and bH in the bc1 Complex. J. Biol. Chem., 278:36191–201.
Shinkarev, V.P., Kolling, D.R.J., Miller, T.J., and Crofts, A.R. 2002. Modulation of the midpoint potential of the [2Fe-2S] rieske iron sulfur center by Qo occupants in the bc1 complex. Biochemistry, 41:14372–82.