Lumen-side topography of the alpha-subunit of the chloroplast cytochrome b-559.
Removal of the extrinsic 33 kDa polypeptide increased the accessibility to trypsin of a COOH-terminal tridecapeptide epitope of the alpha subunit of cytochrome b-559 (psbE gene product). The sensitivity of the cytochrome epitope to trypsin was not measurably affected by removal of the 16 and 23 kDa extrinsic polypeptides, nor increased by removal of the OEC manganese along with the 33 kDa protein. While protecting alpha-cytochrome b-559 against trypsin, the 33 kDa protein is also proteolyzed, suggesting the possibility of an additional protein component involved in the shielding of the cytochrome. Shielding of the COOH-terminal epitope of alpha-cytochrome b-559 by the OEC 33 kDa protein implies that these COOH-terminal chains of the cytochrome are part of a protein network in the lumen space near the photosystem II reaction center. This network may contain residues that are involved in the binding of essential OEC metal ions.
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Department of Biological Sciences, Purdue University, West Lafayette, IN 47907.
Cramer
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D002734:Chlorophyll; D002736:Chloroplasts / Q000648:ultrastructure*; D003573:Cytochrome b Group; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D008970:Molecular Weight; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D010944:Plants; D011487:Protein Conformation; D014357:Trypsin / Q000494:pharmacology
D003573:Cytochrome b Group; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; C019313:cytochrome b559; D014357:Trypsin