Complex formation between Myo4p–She3p and She2p in the absence of mRNA. Analytical ultracentrifuge runs of She2p (red), a headless Myo4p–She3p construct (green), and the two proteins mixed together (black). She2p sedimented at 5.4 S, the motor construct at 4.5 S, and the complex at 7.5 S. Protein concentration was 7 µM Myo4p–She3p and 7 µM tetrameric She2p. When mixed, each concentration was halved. OD, optical density.