The OxyR oxidative stress transcriptional regulator is a DNA-binding protein that belongs to the LysR-type transcriptional regulators (LTTR) family It has the ability to sense oxidative species inside the cell and to trigger the cell s response activating the transcription of genes involved in scavenging oxidative species In the present study we have overexpressed purified and characterized the predicted OxyR homologue (orf xf1273) of the phytopathogen Xylella fastidiosa This bacterium is the causal agent of citrus variegated chlorosis (CVC) disease caused by the 9a5c strain resulting in economic and social losses The secondary structure of the recombinant protein was analyzed by circular dichroism Gel filtration showed that XfoxyR is a dimer in solution Gel shift assays indicated that it does bind to its own predicted promoter under in vitro conditions However considering our control experiment we cannot state that this interaction occurs in vivo Functional complementation assays indicated that xfoxyR is able to restore the oxidative stress response in an oxyr knockout Escherichia coli strain These results show that the predicted orf xf1273 codes for a transcriptional regulator homologous to E coil OxyR involved in the oxidative stress response This may be important for X fastidiosa to overcome the defense mechanisms of its host during the infection and colonization processes (C) 2010 Elsevier Inc All rights reserved