Reactivity of cytochromes c and f with mutant forms of spinach plastocyanin

Modi, Sandeep; Nordling, Margareta; Lundberg, Lennart; Hansson, Örjan; Bendall, Derek S.

doi:10.1016/0005-2728(92)90068-d

Cited by 106 publications

(84 citation statements)

References 17 publications

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“…Site of Electron Transfer-The electron transfer path between cyt f and plastocyanin has been proposed to include Tyr-83 of plastocyanin (20,21,24,25,27). However, in contrast to previous results with a Y83L mutant, we did not find a decrease of the second-order rate constant relative to wild-type plastocyanin by a factor of 40 but only by a factor not higher than 1.7 at 90 mM NaCl.…”

Section: Does Tyr-83 Play a Significant Role In The Electroncontrasting

confidence: 99%

“…Remarkably, the mutants G10V and G10L and, to a smaller extent, G10M showed an increased second-order rate constant as compared with wild-type plastocyanin, in contrast to the mutants A90L and A90T, which show a diminished rate-constant. In mutant L12A, the electron transfer rate was by a factor of 1.9 smaller than that of the wild type at 90 mM NaCl in agreement with the data of Modi et al (25). DISCUSSION The recognition process of proteins involves the interaction of specific surface regions.…”

Section: Does Tyr-83 Play a Significant Role In The Electronsupporting

confidence: 90%

“…At 25°C the value of the rate constant is 62 ϫ 10 6 M Ϫ1 s Ϫ1 in the presence of 150 mM NaCl. Assuming the same ionic strength dependence of the reaction rate at 5 (see below) and 25°C, this value extrapolates to a rate constant of 185 ϫ 10 6 M Ϫ1 s Ϫ1 at 90 mM NaCl, which is by a factor of 4 faster than that reported for truncated cyt f under these conditions (24,25,27) but comparable to the value of 100 ϫ 10 6 M Ϫ1 s Ϫ1 found recently (29). To analyze the surface regions of plastocyanin involved in the rate-limiting step of the reaction with the cyt bf complex, the role of residues in the hydrophobic and acidic patches of spinach plastocyanin was probed using site-directed mutagenesis.…”

Section: Resultsmentioning

confidence: 56%

“…Lee et al (13) have reported that exclusively mutations of the negative patch of residues 42-45 exerted an effect on the interaction with the solubilized cyt f. On the other hand, Kannt et al (26) found that both acidic patches are involved in this interaction and concluded that binding and not the rate of the intracomplex electron transfer is affected. A substitution of Leu-12 in the hydrophobic patch (25) by Asn and Glu was found to accelerate and slow down the second-order rate constant, respectively, a finding that is not fully understood but may suggest a role of this site. For the interaction with truncated, soluble cyt f, it is widely accepted that the electron is transferred to the copper center of plastocyanin via Tyr-83 (20,24,25,27), which seems to be favored by the high electron density at the thiolate of the copper ligand Cys-84 (31).…”

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confidence: 96%

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Dynamic Interaction of Plastocyanin with the Cytochrome bf Complex

Illerhaus

Altschmied

Reichert

et al. 2000

Journal of Biological Chemistry

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The interaction between plastocyanin and the intact cytochrome bf complex, both from spinach, has been studied by stopped-flow kinetics with mutant plastocyanin to elucidate the site of electron transfer and the docking regions of the molecule. Mutation of Tyr-83 to Arg or Leu provides no evidence for a second electron transfer path via Tyr-83 of plastocyanin, which has been proposed to be the site of electron transfer from cytochrome f. The data found with mutations of acidic residues indicate that both conserved negative patches are essential for the binding of plastocyanin to the intact cytochrome bf complex. Replacing Ala-90 and Gly-10 at the flat hydrophobic surface of plastocyanin by larger residues slowed down and accelerated, respectively, the rate of electron transfer as compared with wild-type plastocyanin. These opposing effects reveal that the hydrophobic region around the electron transfer site at His-87 is divided up into two regions, of which only that with Ala-90 contributes to the attachment to the cytochrome bf complex. These binding sites of plastocyanin are substantially different from those interacting with photosystem I. It appears that each of the two binding regions of plastocyanin is split into halves, which are used in different combinations in the molecular recognition at the two membrane complexes.

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Section: Does Tyr-83 Play a Significant Role In The Electroncontrasting

confidence: 99%

Section: Does Tyr-83 Play a Significant Role In The Electronsupporting

confidence: 90%

Section: Resultsmentioning

confidence: 56%

mentioning

confidence: 96%

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Dynamic Interaction of Plastocyanin with the Cytochrome bf Complex

Illerhaus

Altschmied

Reichert

et al. 2000

Journal of Biological Chemistry

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“…We should however bear in mind that Cyt has to interact also with the cytochrome b 6 f complex, for which the aromatic residue would be required (22,24). In a similar way, Tyr-83 in Pc has been reported to be involved in the interaction with cytochrome f but not with PSI (4,25,26). In this context, Sebban-Kreuzer et al (27) have shown that a tyrosine residue at position 64 is essential for electron transfer between Desulfovibrio vulgaris cytochrome c 553 and its formate dehydrogenase.…”

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confidence: 99%

Site-directed Mutagenesis of Cytochromec 6 from Synechocystissp. PCC 6803

Cerda

Díaz‐Quintana

Navarro

et al. 1999

Journal of Biological Chemistry

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This paper reports the first site-directed mutagenesis analysis of any cytochrome c 6 , a heme protein that performs the same function as the copper-protein plastocyanin in the electron transport chain of photosynthetic organisms. Photosystem I reduction by the mutants of cytochrome c 6 from the cyanobacterium Synechocystis sp. PCC 6803 has been studied by laser flash absorption spectroscopy. Their kinetic efficiency and thermodynamic properties have been compared with those of plastocyanin mutants from the same organism. Such a comparative study reveals that aspartates at positions 70 and 72 in cytochrome c 6 are located in an acidic patch that may be isofunctional with the well known "southeast" patch of plastocyanin. Calculations of surface electrostatic potential distribution in the mutants of cytochrome c 6 and plastocyanin indicate that the changes in protein reactivity depend on the surface electrostatic potential pattern rather than on the net charge modification induced by mutagenesis. Phe-64, which is close to the heme group and may be the counterpart of Tyr-83 in plastocyanin, does not appear to be involved in the electron transfer to photosystem I. In contrast, Arg-67, which is at the edge of the cytochrome c 6 acidic area, seems to be crucial for the interaction with the reaction center.Cytochrome c 6 (Cyt) 1 and plastocyanin (Pc) are soluble metalloproteins, located inside the thylakoid lumen of photosynthetic organisms, that carry electrons from cytochrome b 6 f to photosystem I (PSI), which are both membrane-anchored complexes. Although cyanobacteria and eukaryotic green alga can synthesize both Pc and Cyt, Pc seems to have been able to replace the primitive Cyt along evolution of photosynthetic organisms as the copper-protein is the only electron carrier in higher plants. The two metalloproteins are now well characterized, both at the structural and functional levels. Their threedimensional structures have been solved by x-ray crystallography and NMR spectroscopy in several organisms, and their reaction mechanisms have been widely investigated (see Ref. 1 for a recent review).Alignment of eukaryotic Pc and Cyt molecules according to their dipole moment and surface charge distribution has allowed us the observation of areas in the heme protein similar to those previously reported in Pc: i) a hydrophobic region around the surface-exposed heme edge that could be equivalent to the north patch involving the copper ligand His-87 in Pc, and ii) a negatively charged area in Cyt similar to the east acidic patch around Tyr-83 in Pc (1, 2). It should be noted that such an acidic patch is significantly smaller in the metalloproteins isolated from prokaryotes, namely the cyanobacterium Synechocystis sp. PCC 6803 in which the acidic patch is rather southeast-facing, just below Tyr-87.In eukaryotic systems, site-directed mutagenesis of Pc has supplied relevant information on the role of specific residues in site 1 (or the hydrophobic north pole) and site 2 (or the acidic east face), which both have been propos...

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Cytochromef

Soriano¹,

Smith²

2004

Handbook of Metalloproteins

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Cytochrome f ( f , folium, leaf), a c ‐type cytochrome with a characteristic CysXXCysHis amino acid sequence for heme ligation, is the largest of the four major protein subunits of the membrane‐embedded cytochrome b 6 f complex of oxygenic photosynthesis. It contains 285–86 amino acids, consisting of a soluble 250‐residue domain on the p‐side (positive‐side) or lumen‐side of the membrane, a single trans‐membrane 20‐residue α‐helix, and an n‐ or stromal‐side segment consisting of 15 residues. These domains contain, respectively, the heme prosthetic group and intraprotein electron transfer pathway, the membrane anchor and a short segment that is important in the assembly of the b 6 f complex. The function of the cytochrome f in oxygenic photosynthesis is to act as the terminal electron acceptor in the membrane‐embedded cytochrome b 6 f complex that provides the electron transport connection between the photosystem II and photosystem I reaction centers. Electron transfer through the complex is coupled to proton translocation and generation of a proton electrochemical potential that is utilized to drive the synthesis of ATP through the proton‐motive ATP synthase. These functions of the cytochrome b 6 f complex are analogous to those of the multisubunit cytochrome bc 1 complex (ubiquinol:cytochrome c oxidoreductase) of the mitochondrial respiratory chain and photosynthetic bacteria. Both complexes contain four redox centers with very similar redox and structural properties: a covalently bound c ‐type heme in cytochrome f or c 1 , the 2Fe–2S cluster of the Rieske ISP, and the two noncovalently bound hemes of cytochrome b . The structure properties have been defined in 3.0–3.1 Å structures of the b 6 f complex from a thermophilic cyanobacterium and a green alga. These structures also defined a fifth redox prosthetic group, a novel covalently bound heme, tentatively called heme x . With the exception of the extrinsic cytochromes f and c 1 that, except for the heme‐binding peptide sequence, are completely different, the redox‐active protein subunits of the bc 1 and b 6 f complexes are structurally similar. For the b 6 f complex, structures at the level of atomic resolution (<2 Å) have also been obtained for the p‐side or lumen‐side extrinsic domains of cytochrome f and the Rieske high potential [2Fe–2S] protein, which together constitute approximately 40% of the total mass of the complex.

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Reactivity of cytochromes c and f with mutant forms of spinach plastocyanin

Cited by 106 publications

References 17 publications

Dynamic Interaction of Plastocyanin with the Cytochrome bf Complex

Dynamic Interaction of Plastocyanin with the Cytochrome bf Complex

Site-directed Mutagenesis of Cytochromec 6 from Synechocystissp. PCC 6803

Cytochromef

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