Aim Fusion expression and purification of GST fusion protein of the extra membrane domxin of rat acyl coenzyme A:cholesterolacyltransferase (ACAT, amino acid 480～545). Methods Rat ACAT (amino acide 480～545)amplified by PCR was digested with EcoRI and then subcloned into the expression vector pGEX 2TK to get recombinant plasmid pGEX 2TK/rat ACAT (amino acid 480～545).Upon IPTG induction,GST rat ACAT(amino acid 480～545) was expressed in E.coli. The expressed product was purified with Glutathione Sepharose CL 4B affinity chromatography from cellular lysate. Results SDS PAGE and Western blotting analysis showed that purified GST fusion protein of rat ACAT(amino acid 480～545)was obtained. Conclusion The purification of GST fusion protein of the extra membrane domain of rat ACAT(amion acid 480～545)may be useful in the production of antibody against C terminus of rat ACAT and in the studies of the relationship between the structure of ACAT and it’s functions. 还原