Poster Presentation The 42nd Lorne Conference on Protein Structure and Function 2017

Cooling the debate: Structure determination of the controversial Vps4 AAA+ ATPase oligomer using single particle cryo-electron microscopy (#112)

Lou Brillault 1 , Andrew Whitten 2 , Suzanne Norwood 1 , Mohamed Chami 3 , Kenneth Goldie 3 , Brett Collins 1 , Henning Stahlberg 3 , Ben Hankamer 1 , Alan Munn 4 , Michael Landsberg 5
  1. Institute for Molecular Bioscience, St Lucia, QLD, Australia
  2. Australian Nuclear Science and Technology Organisation, Sydney, NSW, Australia
  3. Center for Cellular Imaging and Nano-Analytics, Biozentrum, The University of Basel, Basel, Switzerland
  4. School of medical science, Griffith University, Southport, QLD, Australia
  5. School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD, Australia

The Vacuolar protein sorting 4 (Vps4) AAA+ ATPase is a key regulator of endosomal sorting complexes required for transport (ESCRTs), protein complexes which are involved in membrane deformation and fission in fundamental biological processes such as the terminal stage of cytokinesis and the biogenesis of multivesicular-bodies. ESCRTs can also be hijacked by a subset of viruses including HIV, Herpes simplex and Ebola during viral budding. The knockdown of Vps4 confers protection against virus infection in live mice, highlighting the total dependence of these viruses on Vps4 and making it an attractive target for the development of next generation of anti-virals. Upon binding of ATP, Vsp4 oligomerises with either a double-ring or a single-ring structure. The exact conformation of the oligomer is however open to debate since several studies found controversial results. Here, we present the study of the yeast Vps4E233Q, a hydrolysis deficient mutant. Our preliminary data using Small Angle X-ray Scattering (SAXS) and Multi Angle Light Scattering (MALLS) suggests that the Vps4E233Q ATP-bound state has a single-ring structure. To confirm these observations, we used cryo-electron microscopy (cryo-EM) and Direct Electron Detectors for high-resolution imaging. We show that using common holey carbon grids coated with a thin amorphous carbon layer improves the distribution of Vsp4 particles and thus significantly facilitates single particle analysis. This technique appears to be crucial for obtaining a near-atomic resolution structure of the Vps4 oligomer and for thus solving the controversy surrounding its structure.