Fig. 7. Electron micrographs of F-actin-Cdc8 complexes. Negative staining of (A) F-actin alone (no tropomyosin), (B) F-actin-Cdc8; note the obliquely oriented strands that are characteristic of tropomyosin (Lehman et al., 1994) (several are indicated with arrows, and are best seen by viewing the figure at a glancing angle). When compared with control F-actin, the actin subunit structure of the decorated filaments appeared less well defined, owing to the binding of additional protein. Occasionally, unbound Cdc8 formed very narrow but elongated and continuous filaments, visible in samples of F-actin and Cdc8 tropomyosin (not shown). Bar, 50 nm.