SAR1a gene homolog 1, also known as SAR1A, belongs to the small GTPase superfamily. Sar1 is an essential component of COPII vesicle coats involved in export of cargo from the ER. The GTPase activity of Sar1 functions as a molecular switch to control protein-protein and protein-lipid interactions that direct vesicle budding from the ER. GDP-bound Sar1 interacts with the membrane-bound exchange factor Sec12 and exchanges its bound GDP for GTP. Recombinant human SAR1A, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.