(A) The elution profile of purified MgtE by size exclusion chromatography (SEC) on a Superdex 200 GL 10/300 column (black solid line), along with a standard sample of bovine serum albumin (BSA) (green dashed line). The running buffer was 20 mM HEPES-NaOH (pH 6.1), 100 mM NaCl, and 1 mM DDM. The elution volumes were 11.6 mL for purified MgtE, 14.1 mL, 12.3 mL, and 11.1 mL for the BSA monomer, dimer, and tetramer, respectively. (B) Estimated distribution coefficients (Kav) from the elution volume in (A) were plotted against logarithmic molecular weight (M.W.). The solid line is the best fit function as indicated in the graph of plots of the BSA monomer, dimer, and tetramer. The estimated apparent M.W. of purified MgtE (Kav = 0.23) is approximately 160 kDa, suggesting that the purified MgtE, whose theoretical M.W. is 50 kDa, exists as a dimer in DDM micelles, as the apparent M.W. of DDM micelles is 60 kDa.