E1841K strengthens antiparallel interactions and results in overassembly of filaments in vitro. (A) Diagram depicting NMIIA folded monomer conformation and antiparallel association state. (B-E) Electron micrographs of WT and mutant NMIIA molecules in the disassembled state. Inset pie charts indicate the proportion of molecules in the folded monomer or antiparallel dimer state. Representative class averages of each type are shown alongside. Scale bars, 50 nm. (F-I) Representative electron micrographs of NMIIA bipolar filaments in the assembled state. Scale bar, 100 nm. Scatterplot representing median and interquartile range of filament length (J) and filament width (K). n = 100 filaments for each sample. Image acquisitions were performed with JEOL 1200EX electron microscope equipped with an AMT XR-60 CCD camera. Image alignments were done with SPIDER software, and quantifications were done with Fiji.