On the Spatial Organization of Hemes and Chlorophyll in Cytochrome b 6 f

Schoepp, Barbara; Chabaud, Elodie; Breyton, Cécile; Vermeglio, André; Popot, Jean‐Luc

doi:10.1074/jbc.275.8.5275

Cited by 24 publications

(36 citation statements)

References 61 publications

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“…A light-dark difference spectrum of flash-induced absorbance changes in the region at 540 -570 nm clearly shows the absorbance changes to consist of contributions from both cytochromes f (␣-band maximum, 556 nm) and c 6 (␣-band maximum, 553 nm) (data not shown). The observations in this study that (i) deletion of 2 residues at two different positions in the hinge region produced similar effects on the kinetics of cytochromes f and c 6 and (ii) the retardation of the cytochrome f/c 6 reduction and the loss of its sensitivity to inhibitors in mutant ⌬G51-52 could be fully reverted by reinsertion of 2 Gly residues at a second site between Pro 45 and Ser 46 in a "restoration mutant," ϩ2G-⌬2G (Fig. 4 and Table II; discussed below), show that the flash-induced absorbance change in this region is fully attributed to the electron transfer activity of the b 6 f complex.…”

Section: Resultsmentioning

confidence: 62%

“…A smaller amplitude would allow decreased flexibility and smaller conformational constraints in the hinge region. An important structure difference between the b 6 f and bc 1 complexes is that the electron acceptors of the ISP, cytochromes f and c 1 , respectively, are completely different in sequence and structure (10,11) and heme orientation (43)(44)(45)(46). A close orientation of the cytochrome f heme to the ISP [2Fe-2S] cluster would eliminate the necessity of large-scale ISP movement; on the other hand, a steric constraint from cytochrome f on the free space for ISP movement would prevent large-scale ISP movement, although a significant displacement of the ISP [2Fe-2S] cluster from the quinol of the Q p site is still required for a bifurcated electron transport chain in both cases (7).…”

Section: Discussionmentioning

confidence: 99%

“…With 4 -7 glycine residues in the sequence, the ISP hinge region in the b 6 f complex is predicted to be structure-less and more flexible than that in the bc 1 complex (Table I). Further increases in flexibility or length caused by changing Pro 44 and Pro 45 , which are conserved at the N-terminal end of the hinge region but absent in the bc 1 sequences, to 2 Ala residues in mutant P44A/ P45A or Ser 46 and Ser 47 to 2 Gly residues in mutant S46G/ S47G or by insertion of 4 extra Gly residues in mutant ϩ4Gly (resulting in a total of 9 Gly residues in the "hinge" region) had no effect on the activity of the complex. These mutants showed an electron transfer activity (t1 ⁄2 of cytochrome f/c 6 reduction ϭ 3.1-5.2 ms) similar to that of the wild type (t1 ⁄2 of cytochrome f/c 6 reduction ϭ 4 ms) (Fig.…”

Section: Consequences Of Increased Flexibility and Length Of The Hingmentioning

confidence: 99%

“…4 and Table II). A conformationally inflexible mutant was made by substitution of 2 additional proline residues for Ser 46 and Ser 47 in mutant 6Pro, resulting in a linker region with 8 Pro residues (including the native Pro 44 and Pro 45 residues) (Table II). There was a decrease in activity associated with this mutant, but the 2.4-fold decrease in the electron transfer rate (t1 ⁄2 of cytochrome f/c 6 reduction ϭ 9.6 ms) (Fig.…”

Section: Parts a And B)mentioning

confidence: 99%

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Functional Insensitivity of the Cytochrome b6f Complex to Structure Changes in the Hinge Region of the Rieske Iron-Sulfur Protein

Yan¹,

Cramer

2003

Journal of Biological Chemistry

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Structure analysis of the cytochrome bc 1 complex in the presence and absence of Q p quinol analog inhibitors implied that a large amplitude motion of the Rieske iron-sulfur protein (ISP) is required to mediate electron transfer from ubiquinol to cytochrome c 1 . Studies of the functional consequences of mutagenesis of an 8-residue ISP "hinge" region in the bc 1 complex showed it to be sensitive to structure perturbation, implying that optimum flexibility and length are required for the large amplitude motion. Mutagenesis-function analysis carried out on the ISP hinge region of the cytochrome b 6 f complex using the cyanobacterium Synechococcus sp. PCC 7002 showed the following. (i) Of three petC genes, only that in the petCA operon codes for functional ISP.(ii) The function of the complex was insensitive to changes in the hinge region that increased flexibility, decreased flexibility by substitutions of 4 -6 Pro residues, shortened the hinge by a 1-residue deletion, or elongated it by insertion of 4 residues. The latter change increased sensitivity to Q p inhibitors, whereas deletion of 2 residues resulted in a loss of inhibitor sensitivity and a decrease in activity, indicating a minimum hinge length of 7 residues required for optimum binding of ISP at the Q p site. Thus, in contrast to the bc 1 complex, the function of the b 6 f complex was insensitive to sequence changes in the ISP hinge that altered its length or flexibility. This implies that either the barriers to motion or the amplitude of ISP motion required for function is smaller than in the bc 1 complex.

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Section: Resultsmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Section: Consequences Of Increased Flexibility and Length Of The Hingmentioning

confidence: 99%

Section: Parts a And B)mentioning

confidence: 99%

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Functional Insensitivity of the Cytochrome b6f Complex to Structure Changes in the Hinge Region of the Rieske Iron-Sulfur Protein

Yan¹,

Cramer

2003

Journal of Biological Chemistry

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“…This is most probably due to the small signal sizes as well as to the spectral overlap of b-and c-hemes in these enzymes (13)(14)(15). LD by contrast, has proven to be a good alternate method to determine the orientation of hemes in the case of purple bacterial reaction centers (16 -19) and Cyt b 6 f complex (20). The porphyrin electronic transitions, which produce the ␣, ␤, and ␥ optical bands, are in fact ideal for molecular orientation studies, since the polarization ratio (LD/A) for a linear absorber can be related to the orientation of the X and Y axis in the porphyrin plane (21,22) along the X and Y Fe-pyrrole ring directions (23,24) relative to the orientation axis.…”

mentioning

confidence: 99%

Relative Orientation of the Hemes of the Cytochromebc 1 Complexes from Rhodobacter sphaeroides, Rhodospirillum rubrum, and Beef Heart Mitochondria

Schoepp¹,

Breton²,

Parot³

et al. 2000

Journal of Biological Chemistry

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The orientation of the chromophores in the cytochrome bc 1 of Rhodospirillum rubrum, Rhodobacter sphaeroides, and beef heart mitochondria is reported. The combination of redox-resolved absorption spectrophotometry and linear dichroism experiments at low temperature allows the determination of the orientation of the three hemes with respect to the membrane plane. The orientations of the b H -and b L -hemes of the R. sphaeroides and beef heart mitochondrial complexes are similar to those determined by crystallographic studies of the mitochondrial cytochrome bc 1 . On the other hand the orientations of the b-hemes of the R. rubrum complex lead to the conclusion that the b H -heme is more perpendicular to the membrane plane than the b L -heme. This could be explained by a specific organization of the b-hemes due to subunit composition of the complex or, alternatively, to a different spatial position of the heme transitions with respect to the porphyrin macrocycle compared with the other complexes. Moreover, our results demonstrate a different orientation of the heme c 1 of the three studied complexes in comparison to crystallographic studies. This difference may arise from the above hypothesis on the transitions of the heme or from flexibility of this subunit in function of its redox state.The quinol-cytochrome c (or -plastocyanin) oxidoreductases (cytochrome bc 1 -b 6 f complexes) are a ubiquitous class of enzymes found in mitochondrial and bacterial respiratory chains, as well as in the green plant and bacterial photosynthetic chains (for reviews see also Refs. 1-4). These enzymes couple the two-electron oxidation of quinol (ubi-, mena-, or plasto-) and the one-electron reduction of cytochrome (Cyt) 1 c (or Cyt c 2 , HiPIP, plastocyanin) to the electrogenic translocation of protons across the membrane bilayer. These complexes therefore contribute to the electrochemical proton gradient that drives ATP synthesis.The catalytic heart of the enzyme consists of three subunits, Cyt b, Cyt c 1 , and the iron sulfur protein (termed the Rieske protein) that carry four redox centers. The Cyt b subunit contains a high potential and a low potential b-type heme (termed b H and b L , respectively); the Cyt c 1 subunit contains a c-type heme, and the Rieske protein contains a 2Fe-2S cluster. The complete atomic structure of the mitochondrial enzyme from two species has recently been published (5, 6), but no such structure is presently available for any of the bacterial counterparts. For structural and functional studies of the Cyt bc 1 complex, the photosynthetic bacteria provide, however, several experimental advantages as follows: (i) the bacterial enzyme shows a much simpler organization than the mitochondrial enzyme. Although the mitochondrial Cyt bc 1 complex contains 11 subunits (the functions of which are mostly unknown except those of the catalytic one), the complex from Rhodobacter (Rb.) sphaeroides is reduced to four subunits (7,8), and the enzyme from Rhodospirillum (Rs.) rubrum represents the simplest composition with...

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The Ternary Complex of Cytochrome f and Cytochrome c: Identification of a Second Binding Site and Competition for Plastocyanin Binding

et al. 2002

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The complex of yeast cytochrome c and cytochrome f from the cyanobacterium Phormidium laminosum was investigated by NMR spectroscopy. Chemical shift perturbation analysis reveals that residues around the haem edge of cytochrome c are involved in the complex interface. Binding curves derived from an NMR spectroscopy titration at 10 mM ionic strength indicate that there are two sites for cytochrome c with binding constants of approximately 2 x 10(4) M(-1) and 4 x 10(3) M(-1). A protein docking simulation with NMR-derived constraints identifies two sites, at the front (Site I) and back faces (Site II) of the haem region of cytochrome f. Site I is homologous to the binding site previously determined for the natural cytochrome f partner plastocyanin. Site II may represent the binding site for the Rieske protein in the cytochrome bf complex. Cytochrome c and plastocyanin are shown to compete for binding at Site I. The competition appears to involve electrostatic screening rather than simple steric occlusion of the binding site.

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On the Spatial Organization of Hemes and Chlorophyll in Cytochrome b 6 f

Cited by 24 publications

References 61 publications

Functional Insensitivity of the Cytochrome b6f Complex to Structure Changes in the Hinge Region of the Rieske Iron-Sulfur Protein

Functional Insensitivity of the Cytochrome b6f Complex to Structure Changes in the Hinge Region of the Rieske Iron-Sulfur Protein

Relative Orientation of the Hemes of the Cytochromebc 1 Complexes from Rhodobacter sphaeroides, Rhodospirillum rubrum, and Beef Heart Mitochondria

The Ternary Complex of Cytochrome f and Cytochrome c: Identification of a Second Binding Site and Competition for Plastocyanin Binding

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