4az2 is a 3 chain structure with sequence from Hirudo medicinalis and Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
HIR3P_HIRME Hirudin is a potent thrombin-specific protease inhibitor. It forms a stable non-covalent complex with alpha-thrombin, thereby abolishing its ability to cleave fibrinogen.