Key Points
- To investigate the structural similarity between the 110-kD subunit of the intestinal microvillar 110K-calmodulin complex and conventional myosin using monoclonal antibodies and domain mapping.
- Evaluated cross-reactivity using monoclonal antibodies against Acanthamoeba myosin II and the avian 110-kD subunit (CX 1-5).
- Performed tryptic digestion of chicken skeletal muscle myosin subfragment-1 (S1) and the 110K-calmodulin complex.
- Mapped ATP-binding sites via photoaffinity labeling and characterized calmodulin-binding domains across tryptic fragments.
- All five 110K monoclonal antibodies cross-reacted with the 25-kD NH2-terminal ATP-binding tryptic fragment of skeletal muscle myosin S1 and a corresponding 36-kD ATP-binding fragment of the 110-kD subunit.
- Tryptic cleavage generated distinct calmodulin-binding fragments (60, 40, 29, and 18 kD) that lacked the myosin head epitopes.
- Only the intact 90-kD tryptic fragment retained both ATP-binding and calmodulin-binding regions, establishing that the myosin-like head and calmodulin-binding sites reside in discrete functional domains.
Structured PICO
PPopulationIntestinal microvillar 110K-calmodulin complex and Acanthamoeba myosin II
IInterventionStructural and immunological characterization using monoclonal antibodies
OOutcomeStructural similarity between the 110-kD subunit and myosin
The study provides evidence that the 110K-calmodulin complex is a myosin, with discrete functional domains for calmodulin binding and the myosin head region.