Myosin VIIA is specifically associated with calmodulin and microtubule-associated protein-2B (MAP-2B)

Myosin VIIA is a motor molecule with a conserved head domain and tail regio n unique to myosin VIIA, which probably defines its unique function in vivo . In an attempt to further characterize myosin VIIA function we set out to identify molecule(s) that specifically associate with it. We demonstrate th at 17 and 55 kDa proteins from mouse kidney and cochlea co-purify with myos in VIIA on affinity columns carrying immobilized anti-myosin VIIA. antibody . N-terminal sequencing and immunoblotting analysis identified the 17 kDa p rotein as calmodulin, whereas MS and immunoblotting analysis identified the 55 kDa protein as microtubule-associated protein-2B (MAP-2B). Myosin VIIA can also be co-immunoprecipitated from kidney homogenate using anti-calmodu lin or anti-MAP2 (recognizing isoforms 2A and 2B) antibodies, confirming th e strong association between calmodulin and myosin VIIA and between MAP-2B and myosin VIIA. Myosin VIIA binds to calmodulin with an apparent K-d of 10 (-9) M. Scatchard analysis of the binding of myosin VIIA to MAP-2B provided evidence for two binding sites, with K-d values of 10(-10) and 10(-9) M, w hich have been mapped to medial and C-terminal tail domains of myosin VIIA. The characterization of the interaction of calmodulin and MAP-2B with myos in VIIA provides new insights into the function of myosin VIIA.