A. His-tagged human Atg4A, Atg4B and Atg4C, and GST-tagged Atg4D were expressed in E. Coli, and purified using Ni2+-NTA resins, or glutathione sepharose, respectively. B. Four human Atg8 homologues were fused with the His tag at the N-terminus and GST at the C-terminus, expressed in E. Coli and purified using Ni2+-NTA resins. Recombinant proteins were separated by SDS-PAGE and stained with CBB for quantification by densitometry.