A, calorimetric profile of UDP-GlcA binding to K4CP. The reaction
cell contained a solution of K4CP (1. 4 ml and 124.8 μm) in 25
mm HEPES buffer (pH 7.5) containing 20 mm
MnCl2, 0.1 m NaCl, and 1 mm CaCl2.
The syringe contained 1 mm UDP-GlcA in the same buffer. Top
panel, raw calorimetric data obtained from the injection of 3 μl
aliquots of UDP-GlcA at 3-min intervals. The lower panel shows the
integrated binding isotherm with the experimental points (▪) and best
fit. B, calorimetric profile of UDP-GalNAc binding to K4CP.
C, calorimetric profile of UDP-GlcA binding to the K4CP mutant
construct 239ACA241. D, gel showing the purity
of K4CP used in ITC experiments and enzyme assays. The first lane
contains the SeeBlue Plus 2 prestained molecular marker (Invitrogen), and the
second lane contains purified K4CP.