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Intramolecular electron transfer in blue copper proteins
RBDOX BIOCHEMISTRY
217
6039
ELECTRON TRANSFER IN FLAVOCYTOCHROME b2: INVESTIGATIONS USING SITE-DIRECTED MUTAGENESIS. S.A.White,C.Miles, M.T.Black, G.A. Reid andS.K.Chapman,Edinburgh University, EdinburghEH9 355, SCOTLAND. Flavocytochromeb2 from bakers' yeast isa tetramerof identical subunits with M, 57,500. Eachsubunit contains flavin mononucleotide (FMN) and protoheme IX prosthetic groups in two functionally distinct domains, the crystal strucure of the enzyme has been solved.Theenzyme catalyzes the oxidationof L-lactate to pyruvateand transfers electrons directly to cytochrome c [l]. We have generateda number of site-directed mutant enzymes in order to probe the electron transfer from lactate + flavin, flavin + heme and heme + cytochrome c. The results of these studies have yielded important mechanistic information. [l]G.A. Reid, S. White, M.T. Black, F. Lederer, F.S.Mathews and S.K.Chapman, Eur.J.Biochem., _178, 329 (1988).
GJ)40
SPECTROSCOPIC AND RAPID KINETIC STUDIES OF COMPLEX FORMATION AND ELECTRON TRANSFER BETWEEN HYDROXYLAMINE OXIDO-REDUCTASE AND CYTOCHROME c-554 FROM NITROSOMONAS EUROPAEA. D.M., C. Balny and A.B. Hooper, University of Minnesota, St. Paul, MN 55108, USA. Hydroxylamine oxidoreductase (HAO) and cytochrome c-554 (c-554) are soluble cytochromes containing 6-7 and 4 c-type hemes, respectively, per polypeptide chain. HA0 catalyzes the four electron oxidation of hydroxylamine to nitrite. We show here that ferric c-554 forms a stable complex with ferric HA0 which is observable by optical spectroscopy. When rapidly mixed with HA0 (previously reduced with excess hydroxylamine), c-554 is reduced by approximately two electrons at a rate commensurate with hydroxylamine oxidation in viva, thereby suggesting a role for c-554 as the physiological electron acceptor. We have further studied this reduction as a function of [c-554], ionic strength, pH, and temperature.
6041
LIGHT HARVESTING PEPTIDES. S. E. Vitals, Brian M. Peek, Thomas J. Meyer, Bruce S. Erickson. Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290 USA. We are attempting to construct molecular systems that model the role of the reaction center in photosynthesis. These systems provide the opportunity to investigate long range electron/energy transfer as well as the charge separated states resulting from them. Work of this kind has been done with soluble, derivatized polystyrenes which incorporate donor and acceptor sites. However, these systems are difficult to control from a spatial/synthetic standpoint. We have designed three new amino acids which contain in their side chains a chromophore, an electron donor, and an electron acceptor. We have completed a 3-step synthesis of Boc-L-Lys(PTZ)-OH. We have also synthesized the precursors necessary to attach a carboxylic acid variant of Ru(bpy)g2+ to the modified L-Lysine. We have also investigated the photophysical and electrochemical properties of these compounds.
217
6039
ELECTRON TRANSFER IN FLAVOCYTOCHROME b2: INVESTIGATIONS USING SITE-DIRECTED MUTAGENESIS. S.A.White,C.Miles, M.T.Black, G.A. Reid andS.K.Chapman,Edinburgh University, EdinburghEH9 355, SCOTLAND. Flavocytochromeb2 from bakers' yeast isa tetramerof identical subunits with M, 57,500. Eachsubunit contains flavin mononucleotide (FMN) and protoheme IX prosthetic groups in two functionally distinct domains, the crystal strucure of the enzyme has been solved.Theenzyme catalyzes the oxidationof L-lactate to pyruvateand transfers electrons directly to cytochrome c [l]. We have generateda number of site-directed mutant enzymes in order to probe the electron transfer from lactate + flavin, flavin + heme and heme + cytochrome c. The results of these studies have yielded important mechanistic information. [l]G.A. Reid, S. White, M.T. Black, F. Lederer, F.S.Mathews and S.K.Chapman, Eur.J.Biochem., _178, 329 (1988).
GJ)40
SPECTROSCOPIC AND RAPID KINETIC STUDIES OF COMPLEX FORMATION AND ELECTRON TRANSFER BETWEEN HYDROXYLAMINE OXIDO-REDUCTASE AND CYTOCHROME c-554 FROM NITROSOMONAS EUROPAEA. D.M., C. Balny and A.B. Hooper, University of Minnesota, St. Paul, MN 55108, USA. Hydroxylamine oxidoreductase (HAO) and cytochrome c-554 (c-554) are soluble cytochromes containing 6-7 and 4 c-type hemes, respectively, per polypeptide chain. HA0 catalyzes the four electron oxidation of hydroxylamine to nitrite. We show here that ferric c-554 forms a stable complex with ferric HA0 which is observable by optical spectroscopy. When rapidly mixed with HA0 (previously reduced with excess hydroxylamine), c-554 is reduced by approximately two electrons at a rate commensurate with hydroxylamine oxidation in viva, thereby suggesting a role for c-554 as the physiological electron acceptor. We have further studied this reduction as a function of [c-554], ionic strength, pH, and temperature.
6041
LIGHT HARVESTING PEPTIDES. S. E. Vitals, Brian M. Peek, Thomas J. Meyer, Bruce S. Erickson. Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290 USA. We are attempting to construct molecular systems that model the role of the reaction center in photosynthesis. These systems provide the opportunity to investigate long range electron/energy transfer as well as the charge separated states resulting from them. Work of this kind has been done with soluble, derivatized polystyrenes which incorporate donor and acceptor sites. However, these systems are difficult to control from a spatial/synthetic standpoint. We have designed three new amino acids which contain in their side chains a chromophore, an electron donor, and an electron acceptor. We have completed a 3-step synthesis of Boc-L-Lys(PTZ)-OH. We have also synthesized the precursors necessary to attach a carboxylic acid variant of Ru(bpy)g2+ to the modified L-Lysine. We have also investigated the photophysical and electrochemical properties of these compounds.