Tubulin mutants and the results of the single-molecule motility assay. (A) Schematic representation of the dynein–MT complex representing the structural elements likely to be involved in allosteric communication between the MT and the ATPase site in dynein. (B) Positions of charged residues targeted for alanine mutagenesis in the sequences of α- and β-tubulin from yeast S. cerevisiae (Sc), aligned with the corresponding sequences in pig S. scrofa (Ss) tubulin (PDB ID: 1JFF; Löwe et al., 2001). Each of the positively (blue) or negatively (red) charged residues was substituted with alanine. The mutations that resulted in haploid lethality and slow growth in yeast cells are marked by the letters L and S, respectively (Uchimura et al., 2010). (C) Results of the single-molecule motility assay using the two-headed cytoplasmic dynein GST380. Error bars represent the standard error of the mean.