Measurement of nucleotides in the ePL kinase•PLP complexesa.

aePL kinase (130 µM) samples were incubated with different combinations of PL (0.5 mM), PLP (0.5 mM), MgATP (1 mM), MgADP (1 mM) and MgCl2 (0.5 mM) for one hour at 37°C. These samples were then passed through a sizing column and the fractions containing the enzyme were collected and analyzed with respect to PLP and nucleotides content. The values reported in the table are percentages of saturation with respect to enzyme subunits.bn.d.: not detectable with the method employed (minimum detectable level 1.5 µM; see Experimental Procedures for details).cMgCl2 was also omitted from the chromatography equilibration and elution buffer.