Conditional Loss-of-Myosin-II-Function Mutants Reveal a Position in the Tail that Is Critical for Filament Nucleation

摘要: Abstract 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 mapped the coiled-coil tail region of Dictyostelium myosin-II. Strikingly, both mutations affected same arginine residue at position 1880. A single amino acid substitution, R1880P, disrupted dimerization and tetramerization steps filament nucleation. Even charge reversal this position, R1880D, was sufficient inhibit assembly, while other reversals in antiparallel contact suppressed these assembly mutants. The considerable impact small electrostatic forces on nucleation suggests are delicately balanced easily reversible.