Negative staining and electron microscopy of MYH9 mutant tail fragments. Negative staining and electron microscopy reveal aberrant paracrystal morphology in MYH9 mutant tail fragments. The insets show extremely rare examples and represent the best structures observed. The scale bar is 100 nm. (A) The wild-type tail fragment formed paracrystals with expected morphology. They were large and well-ordered and had uniform periodicity throughout the paracrystal. (B) The R1165C tail fragment is unable to form paracrystals or any other type of large assembly. Instead, we found chainlike structures in a random array. On extremely rare occasions, we found faint examples of assemblies (shown in the inset), but they lacked size, uniformity, and periodicity. (C) The R1933Stop tail fragment predominantly formed chainlike structures similar to R1165C; however, a few paracrystallike assemblies were observed (inset). These lacked size, uniformity, and periodicity. (D) For E1841K, chainlike structures were often observed; however, we also found paracrystals with very different morphology compared with wild-type. Not only are these structures very short in length, but they appear to fray apart at the ends. Periodicity can be found only in the central region of some paracrystals (arrowhead). (E) The D1424N tail fragment assembled into paracrystals (the best example is shown), which were wild type in size, but had altered periodicity.