Fig. 1.

Lon assembles into dodecamers as well as hexamers. (A) Catalytically inactive Lon^S679A (24-µM loading concentration) formed hexamers (expected M_R ∼525 kDa) and dodecamers (expected M_R ∼1,050 kDa) in SEC-MALS experiments. The variation in apparent M_R over both peaks suggests that dodecamers and hexamers are in equilibrium. Dashed lines represent an error of 5% in measurement of molecular weight. Chromatography was performed at room temperature in 50 mM Hepes (pH 7.6), 150 mM NaCl, 20 mM MgCl₂, 10% (vol/vol) glycerol, and 0.1 mM TCEP. (B) Concentration-dependent changes in the population of Lon^S679A dodecamers, hexamers, and monomers in SV-AUC c(s_20,w) distributions. Traces at each concentration were offset on the y axis for clarity. Experiments were performed at 20 °C in 50 mM Hepes-KOH (pH 7.5), 150 mM NaCl, 0.01 mM EDTA, 0.1 mM TCEP, 1 mM MgCl₂, and 0.1 mM ATPγS.