Some serpins can spontaneously convert to an inactive latent state. The serpin <a href="//commons.wikimedia.org/w/index.php?title=PAI-1&amp;action=edit&amp;redlink=1" class="new" title="PAI-1 (page does not exist)">PAI-1</a> remains in the active conformation when bound to <a href="//commons.wikimedia.org/w/index.php?title=Vitronectin&amp;action=edit&amp;redlink=1" class="new" title="Vitronectin (page does not exist)">vitronectin</a> (green). However in the absence of vitronectin, PAI-1 can convert to the inactive latent state. The uncleaved RCL (blue, disordered regions as dashed lines) inserts into the A-sheet and the pulls the first β-strand off the C-sheet (yellow). (<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=1OC0%E2%80%8B">1OC0​</a>, <a rel="nofollow" class="external text" href="http://www.rcsb.org/pdb/explore/explore.do?structureId=1DVM">1DVM</a>, <a rel="nofollow" class="external text" href="http://www.rcsb.org/pdb/explore/explore.do?structureId=1LJ5">1LJ5</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>