Figure 6
Oligomeric states of gsYiiM and ecYiiM. (a) Gel-filtration chromatography to analyze the oligomeric states of ecYiiM and gsYiiM. Both BL21-expressed and TP1000-expressed gsYiiM proteins (calculated molecular weight, 24.1 kDa) were eluted immediately before the 17-kDa protein standard, suggesting that gsYiiM is monomeric in solution. gsYiiM protein that was incubated at 60 °C for 30 minutes was also eluted as a monomer peak (Fig. 6b). In contrast, both BL21-expressed and TP1000-expressed ecYiiM proteins (calculated molecular weight, 25.9 kDa) were eluted immediately before the 44-kDa protein standard, suggesting that ecYiiM is dimeric in solution. (b) Gel-filtration chromatography elution profile for the TP1000-expressed gsYiiM protein that was heat-treated at 60 °C for 30 minutes. The heat-treated gsYiiM protein was also eluted as a monomer as was the untreated gsYiiM protein. (c) Dimeric ecYiiMPi structure. The two subunits of the ecYiiM dimer are shown as differently colored ribbons. Two symmetrical dimerization interfaces (labeled “interface” and “interfaceʹ”) are circled in green. (d) Dimerization interface of the ecYiiMPi structure. ecYiiM and ecYiiMʹ chains are shown as orange Cα traces and magenta ribbons, respectively. The dimerization interface residues of ecYiiM and ecYiiMʹ are represented by green and cyan sticks, respectively. (e) Overlays of the gsYiiM monomers (green and cyan) on each chain of the ecYiiMPi dimer (orange and magenta). (f) Tryptophan-based protein denaturation profiles of gsYiiM and ecYiiM in the presence of urea denaturant. Three independent measurements were performed for each of the gsYiiM and ecYiiM proteins.
