title: N-terminal amino acid sequence analysis of small subunits of photosystem I reaction center complex from a thermophilic cyanobacterium, Synechococcus elongatus Nägeli.
abstract: Four small subunits (14, 13, 10, and 8 kDa) of the photosystem I reaction center complex were isolated from a thermophilic cyanobacterium Synechococcus elongatus and their N-terminal amino acid sequences determined. Sequence analysis of the 10-kDa subunit revealed that the distribution of cysteine residues, Cys-X-X-Cys-X-X-Cys-X-X-X-Cys-Pro, is characteristic of bacterial-type ferredoxins, and that its partial sequence is highly homologous to that deduced from the chloroplast gene frx A of liverwort. This indicates that the 10-kDa polypeptide is an apoprotein carrying two iron-sulfur centers, FA and FB, assigned as [4Fe-4S] clusters, which mediated the light-activated transfer of electrons from P700 in photosystem I reaction center complex to soluble ferredoxin. The amino acid sequence of the 14-kDa polypeptide also showed similarity to that of the 20-kDa polypeptide from spinach chloroplast that can be chemically crosslinked with soluble ferredoxin. Thus, the 14-kDa polypeptide appears to be the ferredoxin 'docking' protein.
authors.affiliation: Department of Biology, Faculty of Science, Science University of Tokyo, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Enami
authors.forename: H
authors.initials: H
authors.lastname: Kaiho
authors.forename: H
authors.initials: H
authors.lastname: Izumi
authors.forename: S
authors.initials: S
authors.lastname: Katoh
authors.forename: N
authors.initials: N
authors.lastname: Kotani
authors.forename: C S
authors.initials: CS
authors.lastname: Jone
authors.forename: M
authors.initials: M
authors.lastname: Kamo
authors.forename: A
authors.initials: A
authors.lastname: Tsugita
mesh_terms: D000595:Amino Acid Sequence; D001059:Apoproteins / Q000032:analysis*; D002734:Chlorophyll / Q000302:isolation & purification; D000458:Cyanobacteria / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D005288:Ferredoxins / Q000032:analysis*; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D008970:Molecular Weight; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000302:isolation & purification
chemical_list: D001059:Apoproteins; D005288:Ferredoxins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll