Microtubules are one of the three primary constituents of the eukaryoticcytoskeleton and are constructed from the protein tubulin. FtsZ is a closestructural homologue of tubulin within prokaryotes, and plays an importantstructural role during cell division. This article compares what is known aboutthe structures that these two homologues are able to form in vivo and in vitroand examines the evidence that the water in the immediate vicinity of thestructures, particularly in microtubules, may play an important role in theirformation and stability. The article then examines evidence that this hydrationlayer might help our understanding of how the structures formed by tubulin andFtsZ are stabilised by associated proteins and selected cations. The article thenconsiders recent studies of the charge distribution and dipole moments oftubulin and extends this work to include the electrostatic characteristics ofFtsZ. There is then an examination of the ways in which the electrostaticsimilarities and differences between the two proteins might be related to thesimilarities and differences in the filamentary structures that they form.
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