Comparing the rates and the activation parameters for the forward reaction between the triplet state of zinc cytochrome c and cupriplastocyanin and the back reaction between the zinc cytochrome c cation radical and cuproplastocyanin

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Fältnamn	Indikatorer	Metadata
000		04632naa a2200397 4500
001		oai:DiVA.org:his-9899
003		SwePub
008		140905s1999 \| \|\|\|\|\|\|\|\|\|\|\|000 \|\|eng\|
024	7	a https://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-98992 URI
024	7	a https://doi.org/10.1021/bi98171562 DOI
040		a (SwePub)his
041		a engb eng
042		9 SwePub
072	7	a ref2 swepub-contenttype
072	7	a art2 swepub-publicationtype
100	1	a Ivković-Jensen, Maja M.u Department of Microbiology, University of Iowa, Iowa City, United States / Department of Chemistry, Iowa State University, Ames, United States4 aut
245	1 0	a Comparing the rates and the activation parameters for the forward reaction between the triplet state of zinc cytochrome c and cupriplastocyanin and the back reaction between the zinc cytochrome c cation radical and cuproplastocyanin
264		c 1999-01-14
264	1	b American Chemical Society (ACS),c 1999
338		a print2 rdacarrier
520		a This is a comparative study of the photoinduced (so-called forward) electron-transfer reaction 3Zncyt/pc(II) --> Zncyt+/pc(I), between the triplet state of zinc cytochrome c (3Zncyt) and cupriplastocyanin [pc(II)], and the thermal (so-called back) electron-transfer reaction Zncyt+/pc(I) --> Zncyt/pc(II), between the cation (radical) of zinc cytochrome c (Zncyt+) and cuproplastocyanin [pc(I)], which follows it. Both reactions occur between associated (docked) reactants, and the respective unimolecular rate constants are kF and kB. Our previous studies showed that the forward reaction is gated by a rearrangement of the diprotein complex. Now we examine the back reaction and complare the two. We study the effects of temperature (in the range 273.3-302.9 K) and viscosity (in the range 1.00-17.4 cP) on the rate constants and determine enthalpies (DeltaH), entropies (DeltaS), and free energies (DeltaG) of activation. We compare wild-type spinach plastocyanin, the single mutants Tyr83Leu and Glu59Lys, and the double mutant Glu59Lys/Glu60Gln. The rate constant kB for wild-type spinach plastocyanin and its mutants markedly depends on viscosity, an indication that the back reaction is also gated. The activation parameters DeltaH and DeltaS show that the forward and back reactions have similar mechanisms, involving a rearrangement of the diprotein complex from the initial binding configuration to the reactive configuration. The rearrangements of the complexes 3Zncyt/pc(II) and Zncyt+/pc(I) that gate their respective reactions are similar but not identical. Since the back reaction of all plastocyanin variants is faster than the forward reaction, the difference in free energy between the docking and the reactive configuration is smaller for the back reaction than for the forward reaction. This difference is explained by the change in the electrostatic potential on the plastocyanin surface as Cu(II) is reduced to Cu(I). It is the smaller DeltaH that makes DeltaG smaller for the back reaction than for the forward reaction.
650	7	a NATURVETENSKAPx Biologix Biokemi och molekylärbiologi0 (SwePub)106022 hsv//swe
650	7	a NATURAL SCIENCESx Biological Sciencesx Biochemistry and Molecular Biology0 (SwePub)106022 hsv//eng
653		a Naturvetenskap
653		a Natural sciences
700	1	a Ullmann, G. Matthiasu Institut für Kristallographie, Freie Universität Berlin, Germany4 aut
700	1	a Crnogorac, Milan M.u Department of Microbiology, University of Iowa, Iowa City, United States4 aut
700	1	a Ejdebäck, Mikael,d 1969-u Department of Biochemistry and Biophysics, Lundberg Institute, Göteborg University, Sweden4 aut0 (Swepub:his)ejdm
700	1	a Young, Simonu Department of Biochemistry and Biophysics, Lundberg Institute, Göteborg University, Sweden4 aut
700	1	a Hansson, Örjanu Department of Biochemistry and Biophysics, Lundberg Institute, Göteborg University, Sweden4 aut
700	1	a Kostić, Nenad M.u Department of Microbiology, University of Iowa, Iowa City, United States4 aut
710	2	a Department of Microbiology, University of Iowa, Iowa City, United States / Department of Chemistry, Iowa State University, Ames, United Statesb Institut für Kristallographie, Freie Universität Berlin, Germany4 org
773	0	t Biochemistryd : American Chemical Society (ACS)g 38:5, s. 1589-1597q 38:5<1589-1597x 0006-2960x 1520-4995
856	4	u http://www.bisb.uni-bayreuth.de/PDF/Ivkovic-Jensen1999.Biochem38-1589.pdf
856	4 8	u https://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-9899
856	4 8	u https://doi.org/10.1021/bi9817156

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Av författaren/redakt...: Ivković-Jensen, ...; Ullmann, G. Matt ...; Crnogorac, Milan ...; Ejdebäck, Mikael ...; Young, Simon; Hansson, Örjan; visa fler...; Kostić, Nenad M.; visa färre...

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