Design And Synthesis Of A Series Of Probes Based On 1,3,4-oxadiazole Sulfide Structure

Rice bacterial leaf blight is a worldwide crop bacterial disease whose pathogen is Xanthomonas oryzae pv.Oryzae(Xoo).Due to the increasing resistance of crop pathogens in recent years,several major bactericides such as Bismerthiazol and its analogues being used to control the disease also significantly decreased.1,3,4-oxadiazole derivatives are not only broadly used in the field of medicine,but also have some potential application prospects in the field of pesticides because of their important biological activity.In our previous and recent work,the 1,3,4-oxadiazole thioether compounds showed good inhibitory activity against rice bacterial leaf blight,however,the targets of these compounds are still unknown.Activity-based protein profiling(ABPP)is an important tool for finding targets,identifying target identities and understanding sites of action.Generally,there are two types of small molecule probes used to finding targets including activity-based probes(ABPs)and affinity-based probes(AfBPs).Such an approach combined with proteomics as well as mass spectrometry(MS)can further identify the target.In summary,we designed and synthesized two kinds of small molecule probes whose parental compounds are highly active 1,3,4-oxadiazole thioether compounds previously developed by our group.With the help of these probes,a series of experiments for target identification were successfully established.Among them,the probe 1-3 had a great influence on the activity of the drug and showed little selectivity for the labeling of the rice bacterial leaf blight after introducing the photoreactive groups.On this basis,we further modified the parent structure,designed and synthesized another three small molecule probes 4-6 and a negative control probe NP2.And the bioassay results of Xoo showed that the probe 4 maintained the similar bioactivity to the parent compound after the pre and post modification,which equipped with the basic conditions for ABP.Followed by a series of labeling experiments including probe screening,concentration-dependent experiments,negative control experiments and competitive inhibition experiments,the protein of about 50 kDa was demonstrated as the specific target protein for the interaction between the probe 4 and Xoo.Simultaneously,the data obtained from the pull-down experiments and mass spectrometric(MS)identification further showed that elongation factor Tu(EF-Tu)is the potential target of probe 4.