| Additionally, the step size is much greater than would be indicated by the size of the lever arm on myosin VI. This indicates that the myosin VI does not solely function using the lever arm mechanism that has been demonstrated for myosin V. Given the presence of a unique 53 amino acid insert between the motor domain, the short lever arm of the molecule, and the promiscuity of the step size it is thought that an unfolding and diffusional search may be occurring at some stage of the ATPase cycle of the myosin VI motor. We are therefore studying domain rearrangements under varying nucleotide conditions. This analysis is being conducted in collaboration with the Pehr Harbury lab using the ICAT cysteine labeling reagent (JBiolChem 2002, 277:30968). By analyzing the changes in degree of surface exposure of the 21 native cysteines in the protein, we hope to reveal systematic shifts in tertiary structure that are occurring in a nucleotide-dependent manner. |
