Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.26.268748v1?rss=1 Authors: Chou, S. Z., Pollard, T. D. Abstract: We report high resolution cryo-electron microscopy structures of actin filaments with N-1-pyrene conjugated to cysteine 374 and either ADP (3.2 [A]) or ADP-phosphate (3.0 [A]) in the active site. Polymerization buries pyrene in a hydrophobic cavity between subunits along the long-pitch helix with only minor differences in conformation compared with native actin filaments. These structures explain how polymerization increases the fluorescence 20-fold, how myosin and cofilin binding to filaments reduces the fluorescence and how profilin binding to actin monomers increases the fluorescence. Copy rights belong to original authors. Visit the link for more info