Mixing wild-type and mutant tail fragments. Mixing wild-type and mutant tail fragments demonstrates these mutations have a dominant activity. First, 100 μg wild-type and each mutant tail fragment were mixed in high salt and then dialyzed into low salt to induce paracrystal formation. Scale bar = 100 nm. (A) Wild-type tail fragment alone formed large well-ordered paracrystals with uniform periodicity. (B) Mixing R1165C with wild type, we found a large number of chainlike structures. Occasionally, small assemblies were observed (inset); however, they lacked size and organization. (C) Mixing R1933Stop with wild type, we typically found chainlike structures; however, on rare occasions we observed assemblies. These structures were short with little to no sign of periodicity. (D) Mixing E1841K with wild type, we sometimes found chainlike structures but most often found very short paracrystals with frayed ends—similar to E1841K alone. (E) Mixing D1424N with wild type, we routinely found paracrystals with morphology similar to that of wild type. Periodicity was normal; however, the mixed paracrystals appeared narrower than wild-type ones. Note that this image shows 2 or 3 paracrystals lying next to one another.