Estimation of the Mr of native CMO by nondenaturing PAGE. The standard proteins were α-lactalbumin (Mr 14,200), carbonic anhydrase (Mr 29,000), chicken egg albumin (Mr 45,000), bovine serum albumin monomer (Mr 66,000), dimer (Mr 132,000), and jack bean urease trimer (Mr 272,000). The coefficient of linear correlation for the regression line shown was 0.994. The interpolated Mr of CMO was 135,000.