Characterization of charge separation in membrane spanning protein reaction centers of bacterial photosynthesis

Conference · Tue Jan 01 00:00:00 EST 1991

OSTI ID:5464512

DiMagno, T J; Norris, J R ^[1]; Hanson, D K; Schiffer, M ^[2]; Fleming, G R; Chan, Chi-Kin ^[3]

---

1. Argonne National Lab., IL (United States) Illinois Univ., Chicago, IL (United States). Dept. of Chemistry
2. Argonne National Lab., IL (United States)
3. Illinois Univ., Chicago, IL (United States). Dept. of Chemistry

At room temperature, transfer of an electron from the singlet excited state of the special pair donor ({sup *}P) to the bacteriopheophytin associated with the L subunit (H{sup L}) takes approximately 3 picoseconds. Even though there are two roughly equivalent branches of chromophores related by a pseudo C{sub 2} symmetry axis, electron transfer occurs only down the H{sub L} branch, and not the H{sub M} branch. This paper addresses the issue of unidirectionality of this initial electron transfer by examining the structure of reaction center proteins and through site-directed mutagenesis of these proteins. Since four or five aromatic amino acids are found only in the active branch of many photosynthetic organisms, experiments currently in progress concern addition of these residues to the H{sub M} branch to decrease the asymmetry of electron transport. Alteration of two residues, Phe{sup L181} and Tyr{sup M208}, is shown to influence the initial kinetics of electron transfer, but alteration of these two amino acids is not sufficient to change unidirectionality of the reaction. 21 refs., 1 fig., 2 tabs., (MHB)

• Research Organization: Argonne National Lab., IL (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5464512
• Report Number(s): ANL/CP-72246; CONF-9107162-1; ON: DE91017323
• Resource Relation: Conference: International symposium on charge and field effects in biosystems, Richmond, VA (United States), 21-27 Jul 1991
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
14 SOLAR ENERGY
PHOTOCHEMICAL REACTIONS
REACTION KINETICS
PHOTOSYNTHETIC REACTION CENTERS
MOLECULAR STRUCTURE
PROTEIN STRUCTURE
STRUCTURE-ACTIVITY RELATIONSHIPS
AMINO ACID SEQUENCE
AMINO ACIDS
CHARGE DISTRIBUTION
ELECTRIC CHARGES
ELECTRON TRANSFER
MEMBRANE PROTEINS
MUTAGENESIS
PHENYLALANINE
PHOTOSYNTHETIC BACTERIA
TYROSINE
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
HYDROXY ACIDS
KINETICS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PROTEINS
550200* - Biochemistry
550700 - Microbiology
140505 - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)