The Cover

Ribbon (top) and space-filling (bottom) models of a tubulin heterodimer in lateral (left) and axial (right) orientations. The -subunit is shown in blue and the -subunit is shown in red. Mutations (positions shown in yellow and green) that stabilize microtubules and confer resistance to colcemid and vinblastine are scattered across both - and -tubulin subunits. For details, see 597 in this issue.