Structure and biogenesis of Chlamydomonas reinhardtii photosystem I.
The photosystem I complex of the green alga Chlamydomonas reinhardtii was isolated and fractionated into its two subcomplex components: the core complex (CC I), which contained the reaction center (P-700) and had four polypeptide subunits, and the light-harvesting complex (LHC I) which contained four polypeptides of about 22, 25, 26 and 27 kDa. The 22-kDa apoprotein was isolated as a chlorophyll a and b binding protein. In the isolated photosystem I holocomplex, about ten copies of the 22-kDa LHC I apoprotein are present for each CC I unit. The 22-kDa polypeptide as well as the other three polypeptides of this complex and the subunit II of CC I are translated on 80S cytoplasmic ribosomes, and therefore are coded in the nucleus. During the greening process of the Chlamydomonas reinhardtii y-1 mutant the 22-kDa LHC I polypeptide, which cross-reacts with polyclonal antibodies raised against the Lemna gibba 20-kDa LHC I apoprotein, accumulates in thylakoids at a late stage of their development, and about 2-3 h after the LHC II and CC I subunit II polypeptides have accumulated. Accumulation of the 22-kDa protein during greening is inhibited by cycloheximide but not by chloramphenicol.
Schuster
G
G
Department of Biological Chemistry, Hebrew University of Jerusalem, Israel.
Nechushtai
R
R
Ferreira
P C
PC
Thornber
J P
JP
Ohad
I
I
D002696:Chlamydomonas / Q000032:analysis* / Q000187:drug effects / Q000378:metabolism; D002701:Chloramphenicol / Q000494:pharmacology; D002734:Chlorophyll / Q000302:isolation & purification* / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D045342:Light-Harvesting Protein Complexes; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000302:isolation & purification* / Q000378:metabolism; D014176:Protein Biosynthesis; D012270:Ribosomes / Q000378:metabolism; D013053:Spectrophotometry
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D002701:Chloramphenicol; D003513:Cycloheximide