Method of producing and purifying soluble recombinant COQ5 protein and soluble recombinant COQ5 protein thereof

A recombinant mitochondrial targeting signal (MTS)-truncated coenzyme Q5 homolog (COQ5) protein prepared by the process comprising the steps of:

• providing an Escherichia coli (E. coli) host cell transformed with an expression vector containing DNA fragments that encode the recombinant COQ5 protein, wherein said recombinant COQ5 protein contains a 6× histidine tag at the N-terminus;
• inducing the expression of recombinant COQ5 protein in the E. coli host cell;
• lysing the bacterial cells with a lysis buffer comprising lysozyme and deoxyribonuclease I (DNase I);
• pre-treating the cell lysate with less than 0.2% of an ionic detergent;
• centrifuging the cell lysate for removing insoluble proteins or debris and collecting supernatant containing the recombinant COQ5 protein;
• and
• applying the supernatant to nickel-nitrilotriacetic acid (Ni-NTA) beads under native conditions that lack exposure to urea to obtain purified recombinant COQ5 protein;
• wherein the recombinant COQ5 protein remains soluble during purification and does not become aggregated or form precipitate after purification when protein solution is exchanged with buffer and the protein is concentrated.