153 Davenport Hall
Office: (217) 333-2043
Lab: (217) 333-7407
Fax: (217) 244-6615
Mail to: Department of Biochemistry
419 Roger Adams Lab B-4
600 S Mathews Ave
Urbana, IL 61801
Antony R Crofts
Professor Emeritus of Biochemistry
Professor Emeritus of Biophysics and Computational Biology
Affiliate, Beckman Institute
Bioenergetics and Photosynthesis, Computational Biology, Enzymology, Ion Channels, Membrane Biology, Microbial Physiology, Molecular Evolution, Protein Structure
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
Structure/function relationships in photosynthetic energy conversion; structure of membrane proteins; mechanism of energy conservation; photosynthesis in intact plants; energetics of the biosphere
We use biophysical, spectroscopic, computational, structural and molecular engineering approaches to the study of the mechanism of the bc1 complex. 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. The bc1 complex is central to all major energy conversion pathways. It oxidizes ubiquinol, reduces cytochrome c, and uses the work potential to form the proton gradient that drives ATP synthesis. We study the enzyme from the photosynthetic bacterium Rhodobacter sphaeroides. In membrane vesicles, we can measure kinetics in situ by photoactivation of the photosynthetic reaction center, which generates the substrates for the complex. With crystallographic structures now available, we 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 using kinetic spectrophotometry, and rapid-mix freeze-quench approaches and EPR spectroscopy to trap and measure reaction intermediates, to probe function and topology of the complex, and the detailed mechanism of partial processes. 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) allow us to probe structure local to paramagnetic catalytic intermediates that are not accessible through crystallography. Our current work involves the role of semiquinone intermediates, the pathway for H+ release from catalytic sites through water chains, and electron transfer across the dimer interface that complicates the simple monomeric Q-cycle mechanism. We are studying these using a variety of biophysical, biochemical, computational and molecular engineering approaches. The project also involve several local and international collaborative projects.
A more esoteric interest comes from attempts to quantify global fluxes in the biosphere. This introduces questions about information fluxes, the role of semantic content and its thermodynamic status, leading to deeper philosophical interests.
1. Crofts, A.R. (2007) Life, information, entropy, and time. Complexity, 13, 14-50 (PMC2577055)
2. Crofts, A.R., Holland, J.T., Victoria, D., Kolling D.R.J., Dikanov, S.A., Gilbreth, R., Lhee, S., Kuras, R., and Guergova-Kuras, M. (2008) The Q-cycle reviewed: How well does a monomeric mechanism of the bc1 complex account for the function of a dimeric complex? Biochim. Biophys. Acta, 1777, 1001-1019 (PMC2578832)
3. Kolling, D.R.J., Samoilova, R.I., Shubin, A.A., Crofts, A.R. and Dikanov, S. A. (2009) Proton Environment of Reduced Rieske Iron-Sulfur Cluster Probed by Two-Dimensional ESEEM Spectroscopy. J. Phys. Chem. 113, 653-667 (PMC2773023)
4. Dikanov, S.A., Samoilova, R.I., Kappl, R., Crofts, A.R. and Hüttermann, J. (2009) The reduced [2Fe-2S] clusters in adrenodoxin and ferredoxin share spin density with protein nitrogens, probed using 2D ESEEM. Phys. Chem. Chem. Phys. 11, 6807-6819 (PMC2773023)
5. Lhee, S., Kolling, D. R., Nair, S. K., Dikanov, S. A. and Crofts, A. R. (2010) Modifications of protein environment of the [2Fe-2S] cluster of the bc1 complex: Effects on the biophysical properties of the Rieske iron-sulfur protein and on the kinetics of the complex. J. Biol. Chem. 285, 9233-9248 (PMC2838342)
6. R.I. Samoilova, A.R. Crofts, S.A. Dikanov, Reaction of superoxide radical with quinone molecules, J. Phys. Chem. A, 115 (2011) 11589-11593
7. S. Hong, D. Victoria, A.R. Crofts, Inter-monomer electron transfer is too slow to compete with monomeric turnover in bc1 complex. Biochim. Biophys. Acta, 1817 (2012) 1053-1062.
8. Victoria, D., Burton, R., Crofts, A.R. (2013) Role of the -PEWY-glutamate in catalysis at the Qo-site of the cyt bc1 complex. Biochim. Biophys. Acta 1827, 365-386.
9. Crofts, A. R., Hong, S., Wilson, C., Burton, R., Victoria, D., Harrison, C., Schulten, K. (2013) The mechanism of ubihydroquinone oxidation at the Qo-site of the cytochrome bc1 complex. Biochim. Biophys. Acta 1827, 1362–1377