Characterization of a bacterioferritin comigratory protein family 1-Cys peroxiredoxin from Candidatus Liberibacter asiaticus

To defend against the lethality of the reactive oxygen species (ROS), nature has armed microorganisms with a range of antioxidant proteins. These include peroxiredoxin (Prx) super family proteins which are ubiquitous cysteine-based non-heme peroxidases. The phytopathogenic bacterium Candidatus Liberibacter asiaticus (CLA), an etiological agent of citrus plants diseases, posses many genes for defense against oxidative stress. The bacterioferritin comigratory protein (BCP), a member of Prxs, is part of an oxidative stress defense system of CLA. The key residue of these enzymes is peroxidatic Cys (termed C P SH) which is contained within an absolutely conserved PXXX (T/S) XXC motif. In the present study, a 1-Cys Prx enzyme (CLa-BCP), having C P SH/sulfenic acid cysteine (C-46) but lacking the resolving cysteine (C R SH), was characterized from CLA. The peroxidase activity was demonstrated using a non-physiological electron donor DTT against varied substrates. The protein was shown to have the defensive role against peroxide-mediated cell killing and an antioxidant activity. In vitro DNA-binding studies showed that this protein can protect supercoiled DNA from oxidative damage. To the best of our knowledge, this is the first report on a 1-Cys BCPs to have an intracellular reactive oxygen species scavenging activity.