FIGURE 4.
Interaction of S100Pwt with the IQ domain of IQGAP1 analyzed by SPR. Tagless S100Pwt was immobilized on a CM5 sensor chip and used for analysis of interaction kinetics with the purified IQ domain. A, IQ domain was injected at concentrations of 0.05–1.5 μm and a flow rate of 60 μl/min, and the average binding level at the end of injection (Req) was used for calculation of the steady state affinity. B, steady state affinity determined from the level of binding at equilibrium (Req) as a function of the sample concentration. Calculations were carried out using the BIAevaluation software version 4.1. An approximate dissociation constant of 2e−7 m was calculated for the binding of the IQ domain to S100P. C, Ca2+ dependence of the interaction between the IQ domain and S100Pwt was analyzed by comparison of the signal intensity in the presence or absence of 2.5 μm free Ca2+. RU, response units.