Plastocyanin cytochrome f interaction

Abstract

Spinach plastocyanin and turnip cytochrome f have been covalently linked by using a water-soluble carbodiimide to yield an adduct of the two proteins. The redox potential of cytochrome f in the adduct was shifted by -20 mV relative to that of free cytochrome f, while the redox potential of plastocyanin in the adduct was the same as that of free plastocyanin. Solvent perturbation studies showed the degree of heme exposure in the adduct to be less than in free cytochrome f, indicating that plastocyanin was linked in such a way as to bury the exposed heme edge. Small changes were also observed when the resonance Raman spectrum of the adduct was compared to that of free cytochrome f. The adduct was incapable of interacting with or donating electrons to photosystem I. Peptide mapping and sequencing studies revealed two sites of linkage between the two proteins. In one site of linkage, Asp-44 of plastocyanin is covalently linked to Lys-187 of cytochrome f. This represents the first identification of a group on cytochrome f that is involved in the interaction with plastocyanin. The other site of linkage involves Glu-59 and/or Glu-60 of plastocyanin to as yet unidentified amino groups on cytochrome f. Euglena cytochrome c-552 could also be covalently linked to turnip cytochrome f, although with a lower efficiency than spinach plastocyanin. In contrast, a variety of cyanobacterial cytochrome c-553's and a cyanobacterial plastocyanin could not be covalently linked to turnip cytochrome f.

Analysis of the 1H‐NMR Chemical Shifts of Cu(I)‐, Cu(II)‐ and Cd‐Substituted Pea Plastocyanin

“…Also the reaction of plastocyanin with cytochrome c, acting as a non-physiological substitute for cytochromef, has been studied extensively. From this work it has emerged that PSI probably binds to both the northern and eastern sides of the molecule but reacts via the hydrophobic patch (Anderson et al, 1987;Takabe and Ishikawa, 1989;Nordling et al, 1991;Hervas et al, 1995), while cytochrome f and c bind and react via the acidic patch (Niwa et al, 1980;Augustin et al, 1983;Beoku-Betts et al, 1985;King et al, 1985;Anderson et al, 1987;Morand et al, 1989;Takabe and Ishikawa, 1989;Gross and Curtiss, 1991 ;He et al, 1991 ;Roberts et al, 1991 ;Christensen et al, 1992;Modi et al, 1992a,b;Meyer et al, 1993). The latter reaction complexes appear not to be static; KostiC and co-workers have tound evidence that a fast rearrangement of the partners within the cytochrome .…”

Structural aspects of the cytochromeb 6 f complex; structure of the lumen-side domain of cytochromef

“…6, PC would bind through its acidic regions (residues 42-45 and 59-61 of spinach plastocyanin) on the side of the barrel to the basic region of cyt f around Lys-187, the copper would be at the bottom of the PC barrel in this binding geometry, and Tyr-83 would then be located closer to the heme than Asp-44. It should be noted that covalent cross-linking of the PC-cyt f pair renders it incompetent for intermolecular electron transfer (Qin and Kostic, 1993), and the PC inactive in the reduction of photosystem I (Morand et al, 1989).…”

“…The smaller domain, consisting of residues 169-231, contains Lys-187, previously shown to cross-link to Asp-44 of plastocyanin (Morand et al, 1989;cf. Redinbo et al, this volume), that is solvent-exposed and 28 Å from the heme Fe (Fig.…”

Cytochromes, Iron-Sulfur, and Copper Proteins Mediating Electron Transfer from the Cyt bc1 Complex to Photosynthetic Reaction Center Complexes

“…Chemical cross-linking has implicated the interaction of a negatively charged region of spinach PC with both PS I and Cyt complexes. Specific cross-linking of spinach PC to lysine residues of turnip Cyt ƒ has been found (Morand et al, 1989), while the basic residues of a positively charged region within spinach PsaF have yet to be cataloged (Wynn et al, 1989;Hippler et al, 1989). From this initial analysis, electrostatic interaction between a negatively-charged domain of PC and a positively charged region on the membranebound redox partner has been proposed.…”

“…From this initial analysis, electrostatic interaction between a negatively-charged domain of PC and a positively charged region on the membranebound redox partner has been proposed. The contribution of this type of interaction is likely to be conserved because Euglena Cyt could also be covalently linked to turnip Cyt ƒ (Morand et al, 1989). However, a variety of cyanobacterial Cyt proteins and a cyanobacterial PC could not be crosslinked to turnip Cyt ƒ.…”