FIGURE 9: Two interconvertible forms of bovine tPA with high and low affinity for Pg. The form tPA* possessing low affinity for Pg exists in equilibrium (50:1) with the high affinity form, tPA. It could be speculated that tPA* only is restricted in its ability to bind Pg (binding interactions symbolized by the B site) while remaining catalytically active (active site symbolized by A).
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