[Prokaryotic expression, protein purification and functional verification of human homotypic fusion and vacuole...

Homotypic fusion and vacuole protein sorting(HOPS) is a protein complex consisting of VPS11, VPS16, VPS18, VPS33, VPS39, VPS41 and regulates membrane transport in vivo through membrane fusion mechanisms. The evidence suggests that HOPS complex as a fusion factor, facilitates autophagosome-lysosome fusion. To determine whether the HOPS complex directly interacts with the autophagic SNARE protein STX17 in vitro, the coding sequence of the six genes were amplified from the existing plasmids by PCR, and then ligated to the prokaryotic expression vector pGEX 4T-1-GST or pET-His-NusA. After identification through colony PCR and DNA sequencing, 6 recombinant plasmids were constructed and transferred into Escherichia coli BL21 (DE3). The recombinant proteins were purified by glutathione sepharose 4B and nickel column. We used the tobacco etch virus protease to cut off the GST-tag or His-NusA-tag, to obtain HA-VPS11 protein of about 105 kDa, Flag-VPS16 protein of about 97 kDa, HA-VPS18 protein of about 108 kDa, Flag-VPS33 protein of about 70 kDa, HA-VPS39 protein of about 97 kDa, and Flag-VPS41 protein of about 98 kDa. The function of the purified proteins was verified by in vitro glutathione S-transferases pull-down assay, confirming that autophagic SNARE protein STX17 interacted directly with HOPS components. Our findings provide experimental basis to further study the function and mechanism of HOPS complex in the process of autophagosome-lysosome fusion.