Dyneins are eukaryotic force-generating ATPases responsible for movement along microtubules, driving the beating of cilia and flagella, and key cytoplasmic processes, such as intracellular transport and mitosis. How these complex mechanoenzymes generate force has been unclear. In the February 13 Nature, Stan Burgess and colleagues at the University of Leeds, UK, reveal new structural details of the protein in action that provides further information about the process (Nature, 421:715-718, February 13, 2003).

Burgess et al. used a combination of electron microscopy and image processing to analyze the motions of dynein C — an isoform from the flagella of the alga Chlamydomonas reinhardtii — that provided views of the components of the large protein at an unprecedented level of detail. Dynein is composed of a ring-like motor domain (the head) with two elongated structures, the stalk and the stem, emerging from it and binding the microtubule track...