FIGURE 4.

Effects of complex formation on autoactivation of cathepsin K. A, self-association of pro-hrCatK(WT) measured by dynamic light scattering in PBS at pH 7.4 compared with that in 100 mm sodium acetate at pH 4.0 with (+) or without (−) salt (100 mm NaCl and 1 mm CaCl₂). B, effect of salt condition and C4-S (18 μm) on the rate of autoactivation of pro-hrCatK (4 μm) at pH 4.0. Activity was measured by scanning densitometry of the remained “unactivated” pro-hrCatK bands on SDS-PAGE gel at a given duration of the reaction. The rates of autoactivation were then estimated from the slope of the early phase of the reaction when only ∼20% of substrate converted to product.