The FtsH Protease Heterocomplex in <i>Arabidopsis</i>: Dispensability of Type-B Protease Activity for Proper Chloroplast Development
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- Di Zhang
- Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing 100871, China
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- Yusuke Kato
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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- Lingang Zhang
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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- Masaru Fujimoto
- Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
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- Nobuhiro Tsutsumi
- Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
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- Sodmergen
- Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing 100871, China
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- Wataru Sakamoto
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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<jats:title>Abstract</jats:title> <jats:p>FtsH is an ATP-dependent metalloprotease present as a hexameric heterocomplex in thylakoid membranes. Encoded in the Arabidopsis thaliana YELLOW VARIEGATED2 (VAR2) locus, FtsH2 is one isoform among major Type A (FtsH1/5) and Type B (FtsH2/8) isomers. Mutants lacking FtsH2 (var2) and FtsH5 (var1) are characterized by a typical leaf-variegated phenotype. The functional importance of the catalytic center (comprised by the zinc binding domain) in FtsH2 was assessed in this study by generating transgenic plants that ectopically expressed FtsH2(488), a proteolytically inactive version of FtsH2. The resulting amino acid substitution inhibited FtsH protease activity in vivo when introduced into Escherichia coli FtsH. By contrast, expression of FtsH2(488) rescued not only leaf variegation in var2 but also seedling lethality in var2 ftsh8, suggesting that the protease activity of Type B isomers is completely dispensable, which implies that the chloroplastic FtsH complex has protease sites in excess and that they act redundantly rather than coordinately. However, expression of FtsH2(488) did not fully rescue leaf variegation in var1 var2 because the overall FtsH levels were reduced under this background. Applying an inducible promoter to our complementation analysis revealed that rescue of leaf variegation indeed depends on the overall amount of FtsH. Our results elucidate protein activity and its amount as important factors for the function of FtsH heterocomplexes that are composed of multiple isoforms in the thylakoid membrane.</jats:p>
収録刊行物
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- The Plant Cell
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The Plant Cell 22 (11), 3710-3725, 2010-11-01
Oxford University Press (OUP)