The inactive δ-conformation of the disease-linked antichymotrypsin mutant (L55P). Four residues of the RCL (blue; disordered region as dashed line) are inserted into the top of the A-sheet. Part of the F α-helix (yellow) has unwound and fills the bottom half of the A-sheet. (<span class="plainlinks"><a href="https://en.wikipedia.org/wiki/Protein_Data_Bank" class="extiw" title="w:Protein Data Bank">PDB</a>: <a rel="nofollow" class="external text" href="http://www.rcsb.org/pdb/explore/explore.do?structureId=1QMN">1QMN</a></span>​)
<a href="//commons.wikimedia.org/wiki/User:Evolution_and_evolvability" title="User:Evolution and evolvability">Thomas Shafee</a>
CC BY 4.0
<span class="int-own-work" lang="en">Own work</span>