Figure 6.

(A) Inhibition of biotin–HK binding to cytokeratin. Biotin–HK (20 nM) in the absence or presence of increasing concentrations of purified HK, LK, or factor XII was incubated in 0.01 M sodium phosphate and 0.15 M NaCl (pH 7.4) containing 1% BSA, 0.01% Tween 20, and 50 μM Zn²⁺ in microtiter plate wells that were coated with 1 μg/well cytokeratin. The amount of biotin–HK bound to the microtiter plate wells was determined as indicated in Experimental Procedures. The data presented are the mean ± SEM of three experiments. (B) Biotin–HK (20 nM) in the absence or presence of increasing concentrations of peptides MKBK from domain 4 of kininogens, HKH20 and HVL24 from domain 5 of HK, LDC27 from domain 3 of kininogens, or a control peptide, FNQ15, was incubated in 0.01 M sodium phosphate and 0.15 M NaCl (pH 7.4) containing 1% BSA, 0.01% Tween 20, and 50 μM Zn²⁺ in microtiter plate wells that were coated with 1 μg/well cytokeratin. The amount of biotin–HK bound to the microtiter plate wells was determined as indicated in Experimental Procedures. The data presented are the mean ± SEM of three experiments.