Key result
Arginine 1880 mutations in Dictyostelium myosin-II disrupt filament nucleation and assembly.
The arginine residue at position 1880 in the coiled-coil tail region of Dictyostelium myosin-II is critical for filament nucleation, demonstrating the significant impact of small electrostatic forces on assembly.
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Dictyostelium myosin-II data warrant no clinical extrapolation; leaves open whether tail arginine residues control filament assembly in mammalian cardiac myosin.
Myosin-II must be assembled into filaments to perform its cellular functions. Two conditional loss-of-myosin-II-function mutants were recovered from a previous genetic screen with defects that were mapped to the coiled-coil tail region of Dictyostelium myosin-II. Strikingly, both tail mutations affected the same arginine residue at position 1880. A single amino acid substitution, R1880P, disrupted both the dimerization and tetramerization steps of filament nucleation. Even a single charge reversal at this position, R1880D, was sufficient to inhibit filament assembly, while other single charge reversals in the region of antiparallel contract suppressed these filament assembly mutants. The considerable impact of small electrostatic forces on nucleation suggests that these steps are delicately balanced and easily reversible.
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Moores et al. (1998) studied this question. Myosin-II tail mutations (R1880P, R1880D) was evaluated on Filament nucleation and assembly. Mutations at arginine 1880 (R1880P and R1880D) in the coiled-coil tail region of Dictyostelium myosin-II disrupted filament nucleation and assembly.
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