Key Points
- To investigate the molecular and kinetic functions of regions encoded by alternative exons from the single Drosophila myosin heavy chain gene.
- Purified myosin from the indirect flight muscles of wild-type Drosophila and transgenic flies expressing an embryonic myosin isoform.
- Measured in vitro actin sliding velocity with and without smooth muscle tropomyosin, determined motor step size using optical tweezers, and quantified basal ATPase activity.
- The in vitro actin sliding velocity on the flight muscle isoform was 6.4 µm·s⁻¹ at 22°C, which was 9-fold faster than on the embryonic isoform.
- Binding of smooth muscle tropomyosin to actin increased sliding velocity on the embryonic isoform 6-fold, whereas velocity on the flight muscle isoform slightly decreased.
- Optical tweezer measurements detected no difference in step size between Drosophila and rabbit skeletal myosins, but flight muscle myosin exhibited higher basal ATPase rates than embryonic and rabbit myosins.
Structured PICO
PPopulationWild-type and transgenic Drosophila expressing a major embryonic myosin isoform
IInterventionPurified flight muscle myosin isoform
CComparatorPurified embryonic myosin isoform
OOutcomeIn vitro actin sliding velocity and basal ATPase ratessurrogate
Alternative exons in the Drosophila myosin heavy chain gene significantly influence myosin kinetics, explaining isoform-specific functional differences in vivo.