title: Monoclonal antibodies to the light-harvesting chlorophyll a/b protein complex of photosystem II.
abstract: A collection of 17 monoclonal antibodies elicited against the light-harvesting chlorophyll a/b protein complex which serves photosystem II (LHC-II) of Pisum sativum shows six classes of binding specificity. Antibodies of two of the classes recognize a single polypeptide (the 28- or the 26- kD polypeptides), thereby suggesting that the two proteins are not derived from a common precursor. Other classes of antibodies cross-react with several polypeptides of LHC-II or with polypeptides of both LHC-II and the light-harvesting chlorophyll a/b polypeptides of photosystem I (LHC-I), indicating that there are structural similarities among the polypeptides of LHC-II and LHC-I. The evidence for protein processing by which the 26-, 25.5-, and 24.5-kD polypeptides are derived from a common precursor polypeptide is discussed. Binding studies using antibodies specific for individual LHC-II polypeptides were used to quantify the number of antigenic polypeptides in the thylakoid membrane. 27 copies of the 26-kD polypeptide and two copies of the 28-kD polypeptide were found per 400 chlorophylls. In the chlorina f2 mutant of barley, and in intermittent light-treated barley seedlings, the amount of the 26-kD polypeptide in the thylakoid membranes was greatly reduced, while the amount of 28-kD polypeptide was apparently not affected. We propose that stable insertion and assembly of the 28-kD polypeptide, unlike the 26-kD polypeptide, is not regulated by the presence of chlorophyll b.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D001665:Binding Sites; D002734:Chlorophyll / Q000235:genetics / Q000276:immunology*; D007887:Fabaceae; D001467:Hordeum; D045342:Light-Harvesting Protein Complexes; D010455:Peptides / Q000276:immunology; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology*; D010946:Plants, Medicinal; D011499:Protein Processing, Post-Translational
chemical_list: D000911:Antibodies, Monoclonal; D045342:Light-Harvesting Protein Complexes; D010455:Peptides; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll