The thylakoid lumen protease Deg1 is involved in the repair of photosystem II from photoinhibition in Arabidopsis.
Deg1 is a Ser protease peripherally attached to the lumenal side of the thylakoid membrane. Its physiological function is unknown, but its localization makes it a suitable candidate for participation in photoinhibition repair by degradation of the photosystem II reaction center protein D1. We transformed Arabidopsis thaliana with an RNA interference construct and obtained plants with reduced levels of Deg1. These plants were smaller than wild-type plants, flowered earlier, were more sensitive to photoinhibition, and accumulated more of the D1 protein, probably in an inactive form. Two C-terminal degradation products of the D1 protein, of 16 and 5.2 kD, accumulated at lower levels compared with the wild type. Moreover, addition of recombinant Deg1 to inside-out thylakoid membranes isolated from the mutant could induce the formation of the 5.2-kD D1 C-terminal fragment, whereas the unrelated proteases trypsin and thermolysin could not. Immunoblot analysis revealed that mutants containing less Deg1 also contain less FtsH protease, and FtsH mutants contain less Deg1. These results suggest that Deg1 cooperates with the stroma-exposed proteases FtsH and Deg2 in degrading D1 protein during repair from photoinhibition by cleaving lumen-exposed regions of the protein. In addition, they suggest that accumulation of Deg1 and FtsH proteases may be coordinated.
Kapri-Pardes
Einat
E
Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel.
Naveh
Leah
L
Adam
Zach
Z
D017360:Arabidopsis / Q000201:enzymology* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D008027:Light; D008954:Models, Biological; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D010447:Peptide Hydrolases / Q000378:metabolism; D010641:Phenotype; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000528:radiation effects; D017433:Protein Structure, Secondary; D034622:RNA Interference; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics; D020524:Thylakoids / Q000201:enzymology* / Q000528:radiation effects*
D029681:Arabidopsis Proteins; D045332:Photosystem II Protein Complex; D011994:Recombinant Proteins; D010447:Peptide Hydrolases; C520844:Deg1 protein, Arabidopsis; D012697:Serine Endopeptidases