In the broadest sense, our objective is to understand biological processes and phenomena in terms of physical mechanisms, i.e. on a molecular level. The main problem addressed in this proposal deals with the conversion of electromagnetic energy (light) into chemical energy, i.e. photosynthesis. This process is mediated by an integral membrane protein - pigment complex called the reaction center (RC). Our work focuses on the structural aspects of the RC from the photosynthetic bacterium Rb. sphaeroides and the structural implications on the function of the RC. The mechanisms of electron and proton transfers that take place in the RC are of general importance in all living systems. For instance, the processes that take place in mitochondria (in mammalian cells) can be viewed as the reverse process of photosynthesis utilizing similar mechanisms. Thus, the understanding of electron and proton transfer mechanisms should lead to a deeper understanding of the molecular basis of some metabolic deficiencies. The fields and methodologies used in this proposal are interdisciplinary, ranging from physics to chemistry and molecular biology. Consequently, different techniques and tools are used in our work, e.g. computational methods, X-ray crystallography, optical spectroscopy, magnetic resonance (EPR, ENDOR), protein chemistry and recombinant DNA techniques. The specific problems addressed are: The three-dimensional structure of native and mutant RCs from the photosynthetic bacterium Rb. sphaeroides and the structure of the transient RC-cyt c2 complex. These studies are being pursued by X-ray crystallography, complemented by magnetic resonance techniques. The mechanisms of two electron transfer reactions: k(1)AB(Q-AQB->QAQ-B) and k(2)AB (Q-AQ-B+H+->Q(QBH)-), as well as the protonation of the secondary quinone, QB, are being studied by kinetic optical spectroscopy and site-directed mutagenesis.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM013191-39
Application #
6606904
Study Section
Molecular and Cellular Biophysics Study Section (BBCA)
Program Officer
Whitmarsh, John
Project Start
1976-05-10
Project End
2005-06-30
Budget Start
2003-07-01
Budget End
2005-06-30
Support Year
39
Fiscal Year
2003
Total Cost
$492,368
Indirect Cost
Name
University of California San Diego
Department
Physics
Type
Schools of Arts and Sciences
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Chirino, A J; Lous, E J; Huber, M et al. (1994) Crystallographic analyses of site-directed mutants of the photosynthetic reaction center from Rhodobacter sphaeroides. Biochemistry 33:4584-93
Paddock, M L; Rongey, S H; McPherson, P H et al. (1994) Pathway of proton transfer in bacterial reaction centers: role of aspartate-L213 in proton transfers associated with reduction of quinoneto dihydroquinone. Biochemistry 33:734-45
McPherson, P H; Schonfeld, M; Paddock, M L et al. (1994) Protonation and free energy changes associated with formation of QBH2 in native and Glu-L212-->Gln mutant reaction centers from Rhodobacter sphaeroides. Biochemistry 33:1181-93
Rongey, S H; Paddock, M L; Feher, G et al. (1993) Pathway of proton transfer in bacterial reaction centers: second-site mutation Asn-M44-->Asp restores electron and proton transfer in reaction centers from the photosynthetically deficient Asp-L213-->Asn mutant of Rhodobacter sphaeroides. Proc Natl Acad Sci U S A 90:1325-9
McPherson, P H; Okamura, M Y; Feher, G (1993) Light-induced proton uptake by photosynthetic reaction centers from Rhodobacter sphaeroides R-26.1. II. Protonation of the state DQAQB2-. Biochim Biophys Acta 1144:309-24
Beroza, P; Fredkin, D R; Okamura, M Y et al. (1991) Protonation of interacting residues in a protein by a Monte Carlo method: application to lysozyme and the photosynthetic reaction center of Rhodobacter sphaeroides. Proc Natl Acad Sci U S A 88:5804-8
Durbin, S D; Feher, G (1990) Studies of crystal growth mechanisms of proteins by electron microscopy. J Mol Biol 212:763-74
Calvo, R; Passeggi, M C; Isaacson, R A et al. (1990) Electron paramagnetic resonance investigation of photosynthetic reaction centers from Rhodobacter sphaeroides R-26 in which Fe2+ was replaced by Cu2+. Determination of hyperfine interactions and exchange and dipole-dipole interactions between Cu2+ and QA- Biophys J 58:149-65
Lubitz, W; Isaacson, R A; Okamura, M Y et al. (1989) ENDOR studies of the intermediate electron acceptor radical anion I-. in Photosystem II reaction centers. Biochim Biophys Acta 977:227-32
Allen, J P; Feher, G; Yeates, T O et al. (1988) Structure of the reaction center from Rhodobacter sphaeroides R-26: protein-cofactor (quinones and Fe2+) interactions. Proc Natl Acad Sci U S A 85:8487-91

Showing the most recent 10 out of 25 publications