Figure 2.

(A) K_d values (normalized to the K_d values measured using protein-free vesicles in the same experiment) for binding of DHFR (open circles) and NusDHFR (solid circles) to POPC/MTX-PE/RhoPE/N-(4-maleimidobutyroyl)-PEG₃-POPE (97/0.5/0.02/2.5 molar proportions) vesicles coupled to MBPCys at the indicated ratios of bound protein to lipid. Data are plotted and fitted as log values to ensure appropriate weighting, as the calculated errors of estimation of K_d increased in direct proportion to the value of K_d. (B) Effect of increased ionic strength (250 mM KCl in place of the normal 150 mM KCl) on binding of NusDHFR to vesicles bearing coupled MBPCys at varying surface densities. Data are presented as the ratio of K_d-values measured at 250 mM vs. 150 mM KCl and are scaled to the same axis dimensions as for panel A.