Actin's origins

Anewly determined structure of a filament-forming protein from bacteria is eerily similar to that of eukaryotic actin.The bacterial protein, MreB, was known to affect cell shape in bacteria; Escherichia coli that lack MreB are spherical rather than rod-shaped. In March of this year, Jeffery Errington and colleagues (University of Oxford, UK) reported that filamentous helical structures containing MreB form close to the cell surface.

Fusinita van den Ent and colleagues (MRC Laboratory of Molecular Biology, Cambridge, UK) leapt on this finding. Beginning in March, they showed that purified MreB protein could form filaments. They then quickly crystallized and then solved the structure of MreB. They find that MreB and actin share all major structural elements, with just one small loop inserted into one of the helices of MreB, and they have very similar active...