title: Type I photosynthetic reaction centres: structure and function.
abstract: We review recent advances in the study of the photosystem I reaction centre, following the determination of a spectacular 2.5 A resolution crystal structure for this complex of Synechococcus elongatus. Photosystem I is proving different to type II reaction centres in structure and organization, and the mechanism of transmembrane electron transfer, and is providing insights into the control of function in reaction centres that operate at very low redox potentials. The photosystem I complex of oxygenic organisms has a counterpart in non-oxygenic bacteria, the strictly anaerobic phototrophic green sulphur bacteria and heliobacteria. The most distinctive feature of these type I reaction centres is that they contain two copies of a large core polypeptide (i.e. a homodimer), rather than a heterodimeric arrangement of two related, but different, polypeptides as in the photosystem I complex. To compare the structural organization of the two forms of type I reaction centre, we have modelled the structure of the central region of the reaction centre from green sulphur bacteria, using sequence alignments and the structural coordinates of the S. elongatus Photosystem I complex. The outcome of these modelling studies is described, concentrating on regions of the type I reaction centre where important structure-function relationships have been demonstrated or inferred.
authors.affiliation: School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK. p.heathcote@qmul.ac.uk
authors.forename: Peter
authors.initials: P
authors.lastname: Heathcote
authors.forename: Michael R
authors.initials: MR
authors.lastname: Jones
authors.forename: Paul K
authors.initials: PK
authors.lastname: Fyfe
mesh_terms: D000595:Amino Acid Sequence; D019414:Chlorobi / Q000737:chemistry / Q000378:metabolism; D000458:Cyanobacteria / Q000737:chemistry*; D004579:Electron Transport; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins