Introduction: The initiation factor IF2 has different functions in the initiation of protein translation. Its C-terminal domain interacts strongly with fMet-tRNA. The main objective of this study is to isolate a specific aptamer for IF2 CTD Escherichia coli and Geobacillus stearothermophilus. Methods: A protein expression system based on E. coli BL21 was used. E. coli BL21 was transformed with InfB CTD sequence. Protein induction was performed under different temperatures and IPTG concentration. His-tagged affinity chromatography was used for protein purification since a hexa-His coding sequence was added to the InfB genes. Results: IF2 CTD was purified in high yields and purity. E. coli IF2 fragment protein concentration (558.0 ng/uL) was three times larger than that of G. stearothemophilus (144.6 ng/uL). Purity of both proteins were >95%. A specific aptamer for IF2 CTD G. stearothermophilus was obtained through SELEX. Conclusion: A rapid and efficient protocol for IF2 CTD protein purification has been developed, allowing the production of thermophilic and mesophilic IF2 fragments. The obtained aptamer may serve as a novel antibiotic mechanism in further studies. / Tesis