Sequences in the myosin II tail required for self-association.

The assembly of myosin II molecules into a filament requires the electrostatic interaction of a domain localized toward the carboxyl-terminus of the myosin II tail. However, the precise sequences involved in this interaction are not known. Here we show that the smallest Dictyostelium myosin II fragment that is necessary and sufficient for self-association is a fragment of 294 amino acids that contains four clusters of positively charged and negatively charged residues. Fragments of the same length but which lack one of these positively or negatively charged clusters are incapable of self-assembly. We postulate that this assembly domain is also found in myosin II from other species. Such charged clusters are found in a similar location in rabbit myosin II and are also essential for filament formation.