A 12.5% SDS-PAGE gel shows molecular weight standards (BioRad Precision Plus Protein™, left) and Acs (72 kDa) purified from cells harboring pACS65 (pTEV16), pACS66 (pTEV17), pACS67 (pTEV18), pACS68 (pTEV19), and pACS69 (pTEV20). Numbers above each well correspond to protein purified from cells harboring respective pTEV vectors (e.g., well labeled 16 corresponds to pTEV16).