E63-1, an ecdysone-inducible, EF hand protein, associates with unconventional myosin VI. T. Do , A. Andres. Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Chicago, IL 60611.

   Members of the EF hand superfamily of calcium-binding proteins perform diverse functions in cellular homeostasis, growth, and development. We study a novel member of this superfamily, E63-1, which displays similarity to two other EF hand proteins, calmodulin and myosin light chain. E63-1 is expressed in many different tissues (brain, muscle, gut), but is induced by the steroid hormone, 20-hydroxyecdysone, in the salivary glands. We have taken a biochemical and genetic approach to elucidate the role E63-1 plays in development. Co-immunoprecipitation experiments show that E63-1 associates with unconventional myosin VI. E63-1 co-localizes with myosin VI as well as with actin filaments, suggesting that this EF hand protein may act as a light chain to regulate myosin VI function. To test the hypothesis that E63-1 acts as a light chain, we will present data from a genetic epistasis analysis with another myosin VI light chain, calmodulin.