Abstract: Rab family proteins are key regulators of vesicular traffic in eukaryotic cells. As an important member of theRab family, Rab2 protein has been shown to be involved in various vesicular trafficking processes, and showed functionaldiversity in different cell types and species. In the present study, EoRab2a, Rab2 homology, was obtained fromEuplotes octocarinatu. The universal TGA stop codon appeared at position 66th in the EoRab2a, encoded cysteine in E.octocarinatum, was replaced by TGC by PCR-mediated site-directed mutagenesis. Mutated EoRab2a open readingframe (ORF) was subcloned into expression vector pGEX-6P-1, and the recombinant plasmid pGEX-6P-1-EoRab2a wastransformed into E. coli BL21 (DE3). GST-EoRab2a protein was expressed in E. coli BL21 (DE3) strain by inductionwith 0.1 mmol/L isopropyl ?-D-thiogalactoside for 6 hours at 37℃. GST-EoRab2a was purified by affinity chromatographyand analyzed by SDS-polyacrylamide gel electrophoresis and Coomassie Blue staining. Two BALB/c mice wereimmunized with 80 ?g purified GST-EoRab2a emulsified in complete Freund’s adjuvant and boosted two times with 50?g purified GST-EoRab2a emulsified in incomplete Freund’s adjuvant. The titer of anti-EoRab2a polyclonal antibody(1∶25600) was detected by indirect ELISA assay and the specificity of the antibody was detected by Western blotting.The cellular localization of EoRab2a in E. octocarinatum was determined by immunofluorescence with polyclonal antibodyraised against GST-Rab2a. Localization showed that Eorab2a displayed a dotted pattern in the E. octocarinatumcytoplasm. The results implied that EoRab2a could be involved in trafficking between the endoplasmic reticulum andthe Golgi apparatus in E. octocarinatum.