Sedimentation equilibrium analysis of the molecular weights of GM-CSF, E21R, sGMRα, sβc, and their complexes
| Species . | M (1-vρ) . | v . | MW . | Predicted MW . | Predicted stoichiometry . |
|---|---|---|---|---|---|
| GM-CSF | 3 590 | 0.734 | 13 700 | — | — |
| E21R | 4 050 | 0.734 | 14 300 | — | — |
| sGMRα | 11 800 | 0.706 | 40 700 | — | — |
| sβc | 26 600 | 0.723 | 97 400 | — | — |
| sGMRα plus GM-CSF | 14 600 | 0.718 | 52 700 | 54 400 | 1:1 |
| sGMRα plus E21R | 15 400 | 0.714 | 54 800 | 55 000 | 1:1 |
| sβc plus sGMRα plus GM-CSF | 37 300 | 0.72 | 135 300 | 151 800 | 2:1:1 |
| Species . | M (1-vρ) . | v . | MW . | Predicted MW . | Predicted stoichiometry . |
|---|---|---|---|---|---|
| GM-CSF | 3 590 | 0.734 | 13 700 | — | — |
| E21R | 4 050 | 0.734 | 14 300 | — | — |
| sGMRα | 11 800 | 0.706 | 40 700 | — | — |
| sβc | 26 600 | 0.723 | 97 400 | — | — |
| sGMRα plus GM-CSF | 14 600 | 0.718 | 52 700 | 54 400 | 1:1 |
| sGMRα plus E21R | 15 400 | 0.714 | 54 800 | 55 000 | 1:1 |
| sβc plus sGMRα plus GM-CSF | 37 300 | 0.72 | 135 300 | 151 800 | 2:1:1 |
The buffer used was 150 mM NaCl/50 mM sodium phosphate, pH 7.0, and the temperature was 20°C. The complexes formed between GM-CSF and E21R with sGMRα and between GM-CSF, sGMRα, and sβc were isolated by gel filtration. The initial concentration used for all samples was between 0.40 and 0.47 mg/mL except for E21R, where the starting concentration was 0.2 mg/mL. The reduced molecular weights of the samples, M (1-vρ), were determined by direct fitting of the sedimentation data presented in Figure 5. These values were used to calculate the molecular weight (MW) of the sedimenting species using the partial specific volumes (v) indicated.