Cloning and expression of a new isotype of the peroxiredoxin gene of Chinese cabbage and its comparison to 2Cys-peroxiredoxin isolated from the same plant

A cDNA encoding a newly identified isotype of peroxiredoxin (Prx) was isola ted from a Chinese cabbage flower bud cDNA library and designated CPrxII. D atabase searches using the predicted CPrxII amino acid sequence revealed no substantial homology to other proteins with the exception of the yeast typ e II Prx with which CPrxII shares 27.8% sequence identity, Recombinant CPrx II expressed in Escherichia coli was able to protect glutamine synthetase f rom inactivation in a metal-catalyzed oxidation system and to reduce H2O2 w ith electrons provided by thioredoxin. This specific antioxidant activity o f CPrxII was about 6-fold higher than that of 2Cys-Prx of the same plant. Z n contrast to 2Cys-Prx, which is predominantly expressed in leaf tissue of cabbage seedlings, CPrxII is highly expressed in root tissue as revealed by Northern and Western blot analyses. The CPrxII gene exists as a small mult igene family in the cabbage genome. (C) 1999 Academic Press.