Sulfotyrosine-Mediated Recognition of Human Thrombin by a Tsetse Fly Anticoagulant Mimics Physiological Substrates

Despite possessing only 32 residues, the tsetse thrombin inhibitor (TTI) is among most potent anticoagulants described, with sub-picomolar inhibitory activity against thrombin. Unexpectedly, TTI isolated from fly 2000-fold more active and 180 Da heavier than synthetic recombinant variants. We predicted presence of a tyrosine O-sulfate post-translational modification TTI, prompting us to investigate effect on anticoagulant activity. A combination chemical synthesis functional assays was used reveal that sulfation significantly improved Using X-ray crystallography, we show N-terminal sulfated segment binds basic exosite II thrombin, establishing interactions similar those physiologic substrates, while C-terminal abolishes catalytic This non-canonical mode inhibition, coupled its potency small size, makes an attractive scaffold for design novel antithrombotics.