Flash-photolysis studies of the electron transfer from genetically modified spinach plastocyanin to photosystem I

• Published in: FEBS letters 1991-10, Vol.291 (2), p.327-330
• Main Authors: Nordling, Margareta, Sigfridsson, Kalle, Young, Simon, Lundberg, Lennart G., Hansson, Örjan
• Format: Article
• Language: English
• Subjects: 2-amino-2-hydroxymethylpropane-1, 3-diol; Biological and medical sciences; Electron Spin Resonance Spectroscopy; Electron transfer; Electron Transport; Flash photolysis; Fundamental and applied biological sciences. Psychology; Kinetics; Molecular and cellular biology; Molecular genetics; Mutagenesis, Site-Directed; Oxidation-Reduction; P700; PCR; Photolysis; Photosynthesis; Photosynthetic Reaction Center Complex Proteins - genetics; Photosystem I; Photosystem I Protein Complex; Plants - genetics; Plastocyanin; Plastocyanin - genetics; polymerase chain reaction; PSI; reaction-center chlorophyll; Site-directed mutagenesis; Spinacia oleracea; Tris
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(91)81313-W

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.