Journal Article

The TL29 Protein is Lumen Located, Associated with PSII and Not an Ascorbate Peroxidase

Irene Granlund, Patrik Storm, Maria Schubert, José G. García-Cerdán, Christiane Funk and Wolfgang P. Schröder

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 11, pages 1898-1910
Published in print November 2009 | ISSN: 0032-0781
Published online October 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp134
The TL29 Protein is Lumen Located, Associated with PSII and Not an Ascorbate Peroxidase

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The TL29 protein is one of the more abundant proteins in the thylakoid lumen of plant chloroplasts. Based on its sequence homology to ascorbate peroxidases, but without any supporting biochemical evidence, TL29 was suggested to be involved in the plant defense system against reactive oxygen species and consequently renamed to APX4. Our in vivo and in vitro analyses failed to show any peroxidase activity associated with TL29; it bound neither heme nor ascorbate. Recombinant overexpressed TL29 had no ascorbate-dependent peroxidase activity, and various mutational analyses aiming to convert TL29 into an ascorbate peroxidase failed. Furthermore, in the thylakoid lumen no such activity could be associated with TL29 and, additionally, TL29 knock-out mutants did not show any decreased peroxidase activity or increased content of radical oxygen species when grown under light stress. Instead we could show that TL29 is a lumen-located component associated with PSII.

Keywords: APX4 • Arabidopsis • Heme • Lumen • Thylakoid membrane

Journal Article.  7804 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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