title: The primary structure of a 4.0-kDa photosystem I polypeptide encoded by the chloroplast psaI gene.
abstract: Partial amino acid sequences have been determined for a 4.0-kDa photosystem I polypeptide from barley. A comparison with the sequence of the chloroplast genome of Nicotiana tabacum and Marchantia polymorpha identified the polypeptide as chloroplast-encoded. We designate the corresponding gene psaI and the polypeptide PSI-I. The barley chloroplast psaI gene was sequenced. The gene encodes a polypeptide of 36 amino acid residues with a deduced molecular mass of 4008 Da. The 4.0-kDa polypeptide is N-terminally blocked with a formyl-methionine residue. Plasma desorption mass spectrometry established that the polypeptide is not post-translationally processed except for possible conversion of a methionine residue into methionine sulfone. The hydrophobic 4.0-kDa polypeptide is predicted to have one membrane-spanning alpha-helix and is homologous to transmembrane helix E of the D2 reaction center polypeptide of photosystem II.
authors.affiliation: Department of Plant Physiology, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
authors.forename: H V
authors.initials: HV
authors.lastname: Scheller
authors.forename: J S
authors.initials: JS
authors.lastname: Okkels
authors.forename: P B
authors.initials: PB
authors.lastname: Høj
authors.forename: I
authors.initials: I
authors.lastname: Svendsen
authors.forename: P
authors.initials: P
authors.lastname: Roepstorff
authors.forename: B L
authors.initials: BL
authors.lastname: Møller
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002734:Chlorophyll / Q000235:genetics*; D002736:Chloroplasts / Q000032:analysis*; D001467:Hordeum / Q000032:analysis / Q000235:genetics; D045342:Light-Harvesting Protein Complexes; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000235:genetics*; D010944:Plants / Q000235:genetics*; D010947:Plants, Toxic; D011487:Protein Conformation; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000032:analysis / Q000235:genetics
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll