Flash-photolysis studies of the electron transfer from genetically modified spinach plastocyanin to photosystem I.
Plastocyanin (Pc) has been modified by site-directed mutagenesis at two separate electron-transfer (ET) sites: Leu-12-Glu at a hydrophobic patch, and Tyr-83-His at an acidic patch. The reduction potential at pH 7.5 is decreased by 26 mV in Pc(Leu-12-Glu) and increased by 35 mV in Pc(Tyr-83-His). The latter mutant shows a 2-fold slower intracomplex ET to photosystem I (PSI) as expected from the decreased driving force. The affinity for PSI is unaffected for this mutant but is drastically decreased for Pc(Leu-12-Glu). It is concluded that the hydrophobic patch is more important for the ET to PSI.
Nordling
M
M
Department of Biochemistry and Biophysics, Chalmers University of Technology, Göteborg, Sweden.
Sigfridsson
K
K
Young
S
S
Lundberg
L G
LG
Hansson
O
O
D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010782:Photolysis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D045331:Photosystem I Protein Complex; D010944:Plants / Q000235:genetics*; D010970:Plastocyanin / Q000235:genetics*
D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010970:Plastocyanin