The 60-kDa precursor to the dithiothreitol-sensitive tetrameric protease of spinach thylakoids: structural similarities between the protease and polyphenol oxidase.
The 60-kDa precursor to the 39-kDa dithiothreitol-sensitive protease was purified from photosystem II membranes of spinach. When partially purified 60-kDa protein was stored at 4 degrees C, the protein was degraded to fragments of 39 and 21 kDa. The 39-kDa fragment was suggested to be identical to the 39-kDa protease from effects of dithiothreitol on these polypeptides. The N-terminal amino acid sequences of the 60-kDa protein and the 39-kDa protease were the same, APILPDVEK-, suggesting that the latter was derived from the N-terminal portion of the former. Immunostaining with polyclonal antibodies against the 60-kDa protein indicated that the 60-kDa protein represents the species that occurs in the native thylakoids. These and other structural properties suggest that the protein might be identical to polyphenol oxidase.
Kuwabara
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Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
D000595:Amino Acid Sequence; D004156:Catechol Oxidase / Q000737:chemistry*; D002736:Chloroplasts / Q000201:enzymology*; D002850:Chromatography, Gel; D004229:Dithiothreitol / Q000494:pharmacology*; D010450:Endopeptidases / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry; D045332:Photosystem II Protein Complex; D011498:Protein Precursors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018724:Spinacia oleracea / Q000201:enzymology*
D046911:Macromolecular Substances; D010446:Peptide Fragments; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D011498:Protein Precursors; D004156:Catechol Oxidase; D010450:Endopeptidases; D004229:Dithiothreitol