title: Alteration of the structure and function of photosystem I by Pb2+.
abstract: The toxic effects of Pb(2+) on photosynthetic electron transport were studied in photosystem I (PSI) submembrane fractions isolated from spinach. Structural and spectroscopic analysis using FTIR, fluorescence and X-ray photoelectron spectroscopy (XPS) showed that Pb(2+) binds with proteins via oxygen and nitrogen atoms with an overall binding constant of KPb-PSI=4.9×10(3) (±0.2) M(-1) and the number of bound Pb(2+) cation was 0.9 per PSI complex. Pb(2+) binding altered the protein conformation indicating a partial protein destabilization. Electron transport and P700 photooxidation/reduction measurements showed that the interaction of Pb(2+) cations with PSI produced a donor side limitation of electron transport presumably due to Pb(2+) binding to or in the vicinity of plastocyanin.
authors.affiliation: Groupe de recherche en biologie végétale, Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, Québec, Canada G9A 5H7.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Belatik
authors.forename: Surat
authors.initials: S
authors.lastname: Hotchandani
authors.forename: Heidar-Ali
authors.initials: HA
authors.lastname: Tajmir-Riahi
authors.forename: Robert
authors.initials: R
authors.lastname: Carpentier
mesh_terms: D002413:Cations, Divalent / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D007854:Lead / Q000737:chemistry / Q000494:pharmacology*; D045342:Light-Harvesting Protein Complexes / Q000187:drug effects / Q000502:physiology; D056951:Photoelectron Spectroscopy; D010788:Photosynthesis / Q000187:drug effects; D045331:Photosystem I Protein Complex / Q000187:drug effects* / Q000502:physiology*; D010970:Plastocyanin / Q000737:chemistry; D011487:Protein Conformation / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D018724:Spinacia oleracea
chemical_list: D002413:Cations, Divalent; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D007854:Lead; D010970:Plastocyanin