Mmitochondrial import receptor subunit TOMM20 homolog, also known as TOMM20, belongs to the Tom20 family. The Tom machinery consists of import receptors for the initial binding of cytosolically synthesized preproteins and a general import pore (GIP) for the membrane translocation of various preproteins into the mitochondria. TOMM20 functions as the transit peptide receptor at the surface of the mitochondrion outer membrane and facilitates the movement of preproteins into the TOM40 translocation pore. Recombinant human TOMM20 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.