RAB31, also known as RAB22B, is a 194 amino lipid-anchored protein that localizes to the cytoplasmic side of the cell membrane and belongs to the Rasrelated GTPase superfamily. Expressed at high levels in lung, brain and heart, RAB31 may function in a similar manner to other Rab proteins, namely playing a role in protein transport. Recombinant human RAB31 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.