The association of yeast phosphoglycerate kinase (EC 2.7.2.3)

Abstract

A molecular weight of 40,030 .+-. 830 was estimated for phosphoglycerate kinase in concentrations less than 0.1 g/100 cm3, comparing favorably with expected values from X-ray diffraction measurements but 10% lower than the previously reported molecular weights made at higher concentrations. The s20,w0 was estimated to be 3.12 (.+-. 0.02) .times. 10-13 s and the coefficient had a low concentration dependency giving a g value (concentration-dependency) of 2.3 .+-. 1.6 cm3 .cntdot. g-1. This agrees with previous qualitative observations. By using fluctuation-intensity spectroscopy, the D20,w was estimated to be 7.4 (.+-. 0.2) .times. 10-11 m2 .cntdot. s-1, and this was indistinguishable from the D20,w calculated from ultracentrifuge results. The water of hydration was estimated to be 0.46 g/g of protein. It is inferred from the estimates that phosphogylcerate kinase associates with an interaction coefficient at 20.degree. C for monomer/dimer of between 10-12 cm3 .cntdot. g-1. The ratio of molecular asymmetry (a/b) was estimated to be 2.5 .+-. 0.2 from the values for D20,w and water of hydration. This compares favorably with the ratio from the overall dimensions estimated from X-ray diffraction measurements.