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First published online August 18, 2006; 10.1104/pp.106.085415 Plant Physiology 142:318-332 (2006) © 2006 American Society of Plant Biologists SUMO-Conjugating and SUMO-Deconjugating Enzymes from Arabidopsis1Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
Posttranslational protein modification by the small ubiquitin-like modifier (SUMO) is a highly dynamic and reversible process. To analyze the substrate specificity of SUMO-conjugating and -deconjugating enzymes from Arabidopsis (Arabidopsis thaliana), we reconstituted its SUMOylation cascade in vitro and tested the capacity of this system to conjugate the Arabidopsis SUMO isoforms AtSUMO1, 2, and 3 to the model substrate ScPCNA from yeast (Saccharomyces cerevisiae). This protein contains two in vivo SUMOylated lysine residues, namely K127 and K164. Under in vitro conditions, the Arabidopsis SUMOylation system specifically conjugates all tested SUMO isoforms to lysine-127, but not to lysine-164, of ScPCNA. The SUMO isoforms AtSUMO1 and AtSUMO2, but not AtSUMO3, were found to form polymeric chains on ScPCNA due to a self-SUMOylation process. In a complementary approach, we analyzed both the SUMO isopeptidase activity and the pre-SUMO-processing capacity of the putative Arabidopsis SUMO proteases At1g60220, At1g10570, and At5g60190 using the known SUMO isopeptidases ScULP1, XopD, and ESD4 (At4g15880) as reference enzymes. Interestingly, At5g60190 exhibits no SUMO protease activity but processes the pre-form of Arabidopsis Rub1. The other five enzymes represent SUMO isopeptidases that show different substrate preferences. All these enzymes cleave AtSUMO1 and AtSUMO2 conjugates of ScPCNA, whereas only the putative bacterial virulence factor XopD is able to release AtSUMO3. In addition, all five enzymes cleave pre-AtSUMO1 and pre-AtSUMO2 peptides, but none of the proteins efficiently produce mature AtSUMO3 or AtSUMO5 molecules from their precursors.
1 This work was supported by the Max Planck Society and by grants of the Bundesministerium für Bildung und Forschung (GABI-Trilateral Project "DILEMA"; AZ 0313150) and the Deutsche Forschungsgemeinschaft (SFB 635). The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Hans-Peter Stuible (stuible{at}mpiz-koeln.mpg.de). www.plantphysiol.org/cgi/doi/10.1104/pp.106.085415 * Corresponding author; e-mail stuible{at}mpiz-koeln.mpg.de; fax 49(0)2215062353. Received June 20, 2006; accepted July 14, 2006. This article has been cited by other articles:
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