Citriculture is the second economic activity of the São Paulo State, but several diseases have reduced the productivity and profits in this area. The citric canker is one of the main citrus diseases and it is caused by the phytopathogenic gram-negative bacterium Xanthomonas axonopodis pv. citri (Xac). The complete genome sequencing of Xac (Silva et al., 2002) opened the opportunity for functional genomic studies of the Xac-citrus interaction. On the other hand, the development of structural biology in the post-genomic era has privileged strategies involving attempts of crystallization of a great number of proteins, increasing the probability to obtain the crystal of proteins of interest to work. With this in mind, a library of mutants of Xac was constructed by random insertion of transposon, using the EZ:TN Kit (Epicentre). These mutants were analyzed by individual inoculation in Citrus limonia var. rangpur lime seedlings, and those that presented modified pathogenicity when compared with the standard phenotype of the canker generated by the wild Xac (positive control) had the mutated ORF (Open Read Frame) identified by sequencing. Among the ~100 mutants with modified pathogenicity, six were selected for the expression of the respective recombinant protein in E coli: XAC0789, XAC1201, XAC1927, XAC2047, XAC3225 and XAC3839. The ORFs were cloned using specific primers, with all the amplifications being made with Taq Hi-Fi (Invitrogen). The amplified ORFs were cloned in the expression vector pET SUMO (Invitrogen) and transformed into E. coli (One Shot^â Mach1^TM-T1^R - Invitrogen) for amplification and further introduction in the lineage of E. coli (BL21(DE3) One Shot^â - Invitrogen) for protein expression. We were able to get the expression of protein from ORFs XAC0789 and XAC2047. These proteins are now being submitted to crystallization for structural analysis.