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Three Thioredoxin Targets in the Inner Envelope Membrane of Chloroplasts Function in Protein Import and Chlorophyll Metabolism
Sandra Bartsch, Julie Monnet, Kristina Selbach, Françoise Quigley, John Gray, Diter von Wettstein, Steffen Reinbothe and Christiane Reinbothe
Proceedings of the National Academy of Sciences of the United States of America
Vol. 105, No. 12 (Mar. 25, 2008), pp. 4933-4938
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25461525
Page Count: 6
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Thioredoxins (Trxs) are ubiquitous small proteins with a redox-active disulfide bridge. In their reduced form, they constitute very efficient protein disulfide oxidoreductases. In chloroplasts, two types of Trxs (f and m) coexist and play central roles in the regulation of the Calvin cycle and other processes. Here, we identified a class of Trx targets in the inner plastid envelope membrane of chloroplasts that share a CxxC motif ≈73 aa from their carboxyl-terminal end. Members of this group belong to a superfamily of Rieske iron-sulfur proteins involved in protein translocation and chlorophyll metabolism. These proteins include the protein translocon protein TIC55, the precursor NADPH:protochlorophyllide oxidoreductase translocon protein PTC52, which operates as protochlorophyllide a-oxygenase, and the lethal leaf spot protein LLS1, which is identical with pheophorbide a oxygenase. The role of these proteins in dark/light regulation and oxidative control by the Trx system is discussed.
Proceedings of the National Academy of Sciences of the United States of America © 2008 National Academy of Sciences