title: The location of plastocyanin in vascular plant photosystem I.
abstract: We have studied the binding sites of the electron donor and acceptor proteins of vascular plant photosystem I by electron microscopy/crystallography. Previously, we identified the binding site for the electron acceptor (ferredoxin). In this paper we complete these studies with the characterization of the electron donor (plastocyanin) binding site. After cross-linking, plastocyanin is detected using Fourier difference analysis of two dimensionally ordered arrays of photosystem I located at the periphery of chloroplast grana. Plastocyanin binds in a small cavity on the lumenal surface of photosystem I, close to the center and with a slight bias toward the PsaL subunit of the complex. The recent release of the full coordinates for the cyanobacterial photosystem I reaction center has allowed a detailed comparison between the structures of the eukaryotic and prokaryotic systems. This reveals a very close homology, which is particularly striking for the lumenal side of photosystem I.
authors.affiliation: School of Biological Sciences, University of Exeter, United Kingdom.
authors.forename: Stuart V
authors.initials: SV
authors.lastname: Ruffle
authors.forename: Aziz O
authors.initials: AO
authors.lastname: Mustafa
authors.forename: Ashraf
authors.initials: A
authors.lastname: Kitmitto
authors.forename: Andreas
authors.initials: A
authors.lastname: Holzenburg
authors.forename: Robert C
authors.initials: RC
authors.lastname: Ford
mesh_terms: D001665:Binding Sites; D005288:Ferredoxins / Q000378:metabolism; D008854:Microscopy, Electron; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism* / Q000648:ultrastructure; D045331:Photosystem I Protein Complex; D010970:Plastocyanin / Q000378:metabolism*; D018724:Spinacia oleracea / Q000378:metabolism*
chemical_list: D005288:Ferredoxins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010970:Plastocyanin