FIGURE 1.

Location and alternative sequence choices for the exon 3 region. The exon 3 region (yellow) and the three other variable regions (7, 9, and 11) encoded by Drosophila alternative exons (shades of red) are mapped onto the chicken myosin S1 structure (gray). The exon 3 region is located near the reactive sulfhydrils (orange) and near the point about which the light-chain region (light chains in light gray) pivots in response to ADP release (Bernstein and Milligan, 1997). The blue spheres depict ADP in the active site. The two alternative amino acid sequences of the exon 3 region are shown below the molecular structure. ^*Signifies nonconserved substitutions.