1A21:
reference: Hinge bending within the cytokine receptor superfamily revealed by the 2.4 A crystal structure of the extracellular domain of rabbit tissue factor., Muller YA, Kelley RF, de Vos AM, Protein Sci 1998 May;7(5):1106-15. PMID: 9605315

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).