Leech antihemostatic proteins share the T-knot scaffold, a disulfide-reinforced structural motif

The occcurence of similar topologies among unrelated proteins is an emergin g theme in structural biology. Here we report that the T-knot scaffold, a d isulfide-reinforced structural motif shared by knottins and EGF-like protei ns, is also present in leech antihemostatic proteins. Our finding emphasize s the versatile nature of this small structural motif, representing a compa ct structural unit suitable for the diverse biological functions performed by knottins, EGF-like proteins and leech antihemostatic proteins.