Tropomyosins promote and maintain actin filaments in many cell types and also regulate the interaction of myosin motors with actin. In fission yeast, a single tropomyosin – Cdc8 – localises to the actinomyosin ring that separates cells at mitosis and is essential for its function. Now, Kalomoira Skoumpla and colleagues report that Cdc8's role is broader – it stabilises actin filaments throughout the cell cycle – and that it is regulated by acetylation (see p. 1635). The authors use several techniques to show that Cdc8 localises to cytoplasmic actin filaments throughout the cell cycle, that it is kept at a constant level, and that 80% of it is always acetylated at the N-terminus. Acetylation, they report, increases the affinity of Cdc8 for actin and enhances its ability to regulate the interaction of actin with myosin. Furthermore, Cdc8 polymers adopt a `closed' conformation on actin filaments that inhibits the interaction of myosin with actin. Thus, the authors conclude, acetylation of Cdc8 provides a regulatory mechanism for modulating both actin filament stability and myosin motor activity.