title: Identification of a primary in vivo degradation product of the rapidly-turning-over 32 kd protein of photosystem II.
abstract: The 32 kd photosystem II protein of plant chloroplasts is rapidly turned over in the light. The initial events in the degradation of the 32 kd protein were studied. A 23.5 kd breakdown product was identified in Spirodela oligorrhiza membranes using immunological analysis. The 23.5 kd polypeptide was shown to be derived from the amino-terminal portion of the 32 kd protein using partial proteolytic fingerprinting. An in vivo precursor--product relationship between the 32 kd protein and the 23.5 kd polypeptide was kinetically demonstrated by radiolabeling and pulse-chase experiments. The cleavage site yielding the 23.5 kd polypeptide was localized to a functionally active region (between helices IV and V) of the 32 kd protein. We propose that an alpha-helix-destabilizing 'degradation' sequence, bordered by arginine residues 225 and 238, is involved in the formation of the 23.5 kd polypeptide.
authors.affiliation: Department of Plant Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: B M
authors.initials: BM
authors.lastname: Greenberg
authors.forename: V
authors.initials: V
authors.lastname: Gaba
authors.forename: A K
authors.initials: AK
authors.lastname: Mattoo
authors.forename: M
authors.initials: M
authors.lastname: Edelman
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D010447:Peptide Hydrolases