Identification of the photosystem I antenna polypeptides in barley. Isolation of three pigment-binding antenna complexes.
The light-harvesting antenna of barley photosystem I (LHCI) was isolated from native photosystem I (PSI) complexes and fractionated into three pigment-protein subcomplexes using two consecutive rounds of green gel electrophoresis. Each complex showed a characteristic polypeptide composition and low-temperature fluorescence emission spectrum; they were designated as LHCI-730, LHCI-680A and LHCI-680B. Their four apoproteins of 21, 22, 23 and 25 kDa were purified and NH2-terminal sequences were determined; in the case of the NH2-terminally blocked 25-kDa protein, an internal sequence was obtained after cleavage with endoproteinase Lys-C. This made possible an assignment of the four proteins to the four types (I-IV) of genes coding for chlorophyll a/b proteins of PSI (cab or lha genes). The LHCI-730 complex was isolated as a heterodimer composed of the 21-kDa (LHCI type IV) and the 22-kDa (LHCI type I) polypeptides. Each LHCI-680 complex had a single apoprotein. LHCI-680A consisted of the 25-kDa (LHCI type III) and LHCI-680B of the 23-kDa (LHCI type II) polypeptides. LHCI-680B was associated with the non-pigmented PSI-E subunit, indicating that this protein may function in the binding of this antenna to the reaction centre.
Knoetzel
J
J
Carlsberg Laboratory, Department of Physiology, Copenhagen Valby, Denmark.
Svendsen
I
I
Simpson
D J
DJ
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D001059:Apoproteins / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D001467:Hordeum / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D008970:Molecular Weight; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000302:isolation & purification; D045331:Photosystem I Protein Complex; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid
D000911:Antibodies, Monoclonal; D001059:Apoproteins; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex