Modulation of serpin conformation by cofactors. (a) The structure of native SERPINC1 (PDB code 2ANT) . The partial insertion of the RCL (two residues) into the top of β-sheet A is circled, and the position of the P1 residue is shown (magenta spheres). (b) The structure of the ternary complex between SERPINC1, inactive thrombin (the Ser195Ala mutant) and a synthetic long-chain heparin construct (PDB code 1TB6) . A specific high-affinity pentasaccharide (green) on the heparin interacts with the heparin-binding site on SERPINC1 (on and around helix hD) and promotes expulsion of the RCL (blue arrow) and rearrangement of the P1 residue (magenta spheres).
Law et al. Genome Biology 2006 7:216 doi:10.1186/gb-2006-7-5-216