The aim of this project is to determine the detailed molecular structure of the photosynthetic reaction center from the photosynthetic bacterium Rhodopseudomonas sphaeroides R-26 by studying single crystals of this protein complex through x-ray diffraction. Reaction centers are intrinsic membrane proteins that carry out the initial steps in photosynthetic charge separations. The R. sphaeroides reaction center (Mr about 100,000) contains three protein subunits, four bacteriochlorophylls, two bacteriophenophytins, two ubiquinones, and one nonheme iron. We have grown single crystals of the reaction center, which diffract to beyond 3 angstroms resolution, thus making the determination of structure at atomic resolution possible. We plan to determine structure by using conventional crystallographic methods. The R. spheroides reaction center will serve as a model system to study how transmembrane electron transport is coupled to the production of membrane potential. This reaction center has been studied extensively through both spectroscopic and biochemical methods. The reaction center complex is functional in the crystal, therefore we will have a unique opportunity to correlate spectroscopic results with the three-dimensional structure of the complex. This study will contribute to the understanding of the structure of membrane proteins. The R. spharoides reaction center is only one of three membrane proteins for which the availability of highly ordered crystals makes the determination of detailed structure possible. The correlation of its amino acid sequence with the three-dimensional structure will increase the data base for membrane proteins, thereby markedly enhancing structure prediction efforts for these types of proteins.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM036598-05
Application #
3290905
Study Section
Molecular and Cellular Biophysics Study Section (BBCA)
Project Start
1986-05-01
Project End
1991-04-30
Budget Start
1990-05-01
Budget End
1991-04-30
Support Year
5
Fiscal Year
1990
Total Cost
Indirect Cost
Name
University of Chicago
Department
Type
Organized Research Units
DUNS #
225410919
City
Chicago
State
IL
Country
United States
Zip Code
60637
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Miksovska, J; Kalman, L; Schiffer, M et al. (1997) In bacterial reaction centers rapid delivery of the second proton to QB can be achieved in the absence of L212Glu. Biochemistry 36:12216-26
Valerio-Lepiniec, M; Delcroix, J D; Schiffer, M et al. (1997) A native electrostatic environment near Q(B) is not sufficient to ensure rapid proton delivery in photosynthetic reaction centers. FEBS Lett 407:159-63
Laible, P D; Greenfield, S R; Wasielewski, M R et al. (1997) Antenna excited state decay kinetics establish primary electron transfer in reaction centers as heterogeneous. Biochemistry 36:8677-85
Miksovska, J; Maroti, P; Tandori, J et al. (1996) Distant electrostatic interactions modulate the free energy level of QA- in the photosynthetic reaction center. Biochemistry 35:15411-7
Sebban, P; Maroti, P; Schiffer, M et al. (1995) Electrostatic dominoes: long distance propagation of mutational effects in photosynthetic reaction centers of Rhodobacter capsulatus. Biochemistry 34:8390-7
Sebban, P; Maroti, P; Hanson, D K (1995) Electron and proton transfer to the quinones in bacterial photosynthetic reaction centers: insight from combined approaches of molecular genetics and biophysics. Biochimie 77:677-94
Schiffer, M; Ainsworth, C F; Deng, Y L et al. (1995) Proline in a transmembrane helix compensates for cavities in the photosynthetic reaction center. J Mol Biol 252:472-82
Maroti, P; Hanson, D K; Baciou, L et al. (1994) Proton conduction within the reaction centers of Rhodobacter capsulatus: the electrostatic role of the protein. Proc Natl Acad Sci U S A 91:5617-21
Ermler, U; Michel, H; Schiffer, M (1994) Structure and function of the photosynthetic reaction center from Rhodobacter sphaeroides. J Bioenerg Biomembr 26:5-15

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