Structure, regulation, and diverse functions of archaeal tubulin superfamily proteins — ASN Events
  1. Schedule
  2. Session Four - Microbes
  3. Structure, regulation, and diverse functions of archaeal tubulin superfamily proteins

Structure, regulation, and diverse functions of archaeal tubulin superfamily proteins (#12)

Iain G Duggin 1 , Christopher HS Aylett 2 , James C Walsh 1 3 , Christopher Angstmann 3 , Paul MG Curmi 3 , Katharine A Michie 2 , Qing Wang 2 , Emma M Dawson 1 , Elizabeth J Harry 1 , Lynne Turnbull 1 , Cynthia B Whitchurch 1 , Linda A Amos 2 , Jan Lowe 2
  1. ithree institute, UTS, Ultimo, Sydney, NSW, Australia
  2. MRC Laboratory of Molecular Biology, Cambridge, UK
  3. School of Physics, UNSW, Sydney, NSW, Australia

Tubulin is a major component of the eukaryotic cytoskeleton, controlling cell shape, structure and dynamics, whereas its bacterial homolog FtsZ establishes the cytokinetic ring that constricts during cell division. Although these proteins share a GTP-dependent ability to polymerise into filaments, how such different biological roles of tubulin and FtsZ evolved is unknown. Archaea might provide insights, as these organisms have a prokaryotic cell layout, but are phylogenetically more related to eukaryotes than bacteria.

Whereas bacterial cells contain a single FtsZ, many archaea encode multiple homologs. We found that two of the eight tubulin/FtsZ homologs present in the model archaeon Haloferax volcanii have different roles in cell division. Fluorescence, super-resolution and time-lapse microscopy revealed a dynamic pattern of protein localisation during cell division in which planes of cell division are established orthogonally in successive cell cycles. Furthermore, mathematical modelling implies the existence of an underlying molecular patterning system that uses the cell’s geometry to direct the placement of the division site.

The remaining six tubulin-like proteins in H. volcanii are members of a distinct uncharacterized family more closely related to tubulin. Surprisingly, they were not required for cell division, but two of the CetZs were found to control cell shape. In particular, the conserved CetZ1 plays a key role in the differentiation of the common discoidal cell type into an elongated rod-shaped cell required for motility. CetZ structure-function and cellular localisation studies, using super-resolution microscopy, cryoelectron tomography, and x-ray crystallography, have provided insight into how these proteins might control cell shape. This cell-shape function in prokaryotes is reminiscent of tubulin's role in controlling eukaryotic cell structure, suggesting that the CetZ protein family may resemble an early intermediate in the evolution of the tubulin cytoskeleton*.

  1. *Duggin, I.G., Aylett, C.S., Walsh, J.C., Michie, K.A., Wang, Q., Turnbull, L., Dawson, E.M., Harry, E.J., Whitchurch, C.B., Amos, L.A. and Löwe, J. (2014) CetZ tubulin-like proteins control archaeal cell shape. Nature, In press.