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Tansley Review No. 94 Thioredoxins: structure and function in plant cells

Published online by Cambridge University Press:  01 August 1997

JEAN-PIERRE JACQUOT
Affiliation:
Institut de Biotechnologie des Plantes, URA 1128 CNRS, Université de Paris-Sud, Bâtiment 630, 91405 Orsay Cedex, France
JEAN-MARC LANCELIN
Affiliation:
Laboratoire de RMN Biomoléculaire, ESA 5078 CNRS, Université de Lyon 1 et CPE–Lyon, Bâtiment 308, 69622 Villeurbanne Cedex France
YVES MEYER
Affiliation:
Laboratoire de Physiologie et Biologie Moléculaire des Plantes, UMR 5545 CNRS, Université de Perpignan, 66025 Perpignan Cedex France
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Abstract

Thioredoxins are ubiquitous small-molecular-weight proteins (typically 100–120 amino-acid residues) containing an extremely reactive disulphide bridge with a highly conserved sequence -Cys-Gly(Ala/Pro)-Pro-Cys-. In bacteria and animal cells, thioredoxins participate in multiple reactions which require reduction of disulphide bonds on selected target proteins/enzymes. There is now ample biochemical evidence that thioredoxins exert very specific functions in plants, the best documented being the redox regulation of chloroplast enzymes. Another area in which thioredoxins are believed to play a prominent role is in reserve protein mobilization during the process of germination. It has been discovered that thioredoxins constitute a large multigene family in plants with different subcellular localizations, a unique feature in living cells so far. Evolutionary studies based on these molecules will be discussed, as well as the available biochemical and genetic evidence related to their functions in plant cells. Eukaryotic photosynthetic plant cells are also unique in that they possess two different reducing systems, one extrachloroplastic dependent on NADPH as an electron donor, and the other one chloroplastic, dependent on photoreduced ferredoxin. This review will examine in detail the latest progresses in the area of thioredoxin structural biology in plants, this protein being an excellent model for this purpose. The structural features of the reducing enzymes ferredoxin thioredoxin reductase and NADPH thioredoxin reductase will also be described. The properties of the target enzymes known so far in plants will be detailed with special emphasis on the structural features which make them redox regulatory. Based on sequence analysis, evidence will be presented that redox regulation of enzymes of the biosynthetic pathways first appeared in cyanobacteria possibly as a way to cope with the oxidants produced by oxygenic photosynthesis. It became more elaborate in the chloroplasts of higher plants where a co-ordinated functioning of the chloroplastic and extra chloroplastic metabolisms is required.

Type
Review Article
Copyright
© Trustees of the New Phytologist 1997

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