[Figure 1 from Shih and Rothfield (2006); click on image to enlarge]
Recently, Alex had asked for a mention of the bacterial cytoskeleton, which does deserve mention. As Shih and Rothfield describe, the amino acid sequences of eukaryotic and bacterial cytoskeletal monomers bear minimal resemblance to one another. Their 3-dimensional structures, however, bear striking resemblances – in particular, compare Actin and beta-Tubulin with ParM and BtubA, respectively.
Similarly, these structural homologs share important properties, such as the capacity to self-assemble into filamentous polymers in vitro in the presences of ATP or GTP, and their ability to organize into ordered long-range structures within the cell. Also, they serve comparable cellular functions, including chromosome segregation, cytokinesis, regulation of cell shape, and establishment of cell polarity.
It’s also worth noting, from the viewpoint of the evolutionary continuum between prokaryotes and eukaryotes, that these few proteins are not the whole set of cytoskeletal proteins. They’re just the most studied, and as Shih and Rothfield (2006) point out, there are plenty of others, indicating a range of protein structures that are possible.
- Shih YL, Rothfield L. The bacterial cytoskeleton. Microbiol Mol Biol Rev. 2006 Sep;70(3):729-54.