7M6J

Human Septin Hexameric Complex SEPT2G/SEPT6/SEPT7 by Single Particle Cryo-EM

Summary for 7M6J

• Entry DOI: 10.2210/pdb7m6j/pdb
• EMDB information: 23698
• Descriptor: Septin-2, Septin-6, Septin-7, ... (6 entities in total)
• Functional Keywords: complex, spa, cytoskeleton, cell cycle
• Biological source: Homo sapiens (Human); More
• Total number of polymer chains: 6
• Total formula weight: 265150.91

Authors

Mendonca, D.C.,Pereira, H.M.,van Heel, M.,Portugal, R.V.,Garratt, R.C. (deposition date: 2021-03-25, release date: 2021-07-07, Last modification date: 2024-10-23)

Primary citation

Mendonca, D.C.,Guimaraes, S.L.,Pereira, H.D.,Pinto, A.A.,de Farias, M.A.,de Godoy, A.S.,Araujo, A.P.U.,van Heel, M.,Portugal, R.V.,Garratt, R.C.
An atomic model for the human septin hexamer by cryo-EM.
J.Mol.Biol., 433:167096-167096, 2021

PubMed Abstract: In order to form functional filaments, human septins must assemble into hetero-oligomeric rod-like particles which polymerize end-to-end. The rules governing the assembly of these particles and the subsequent filaments are incompletely understood. Although crystallographic approaches have been successful in studying the separate components of the system, there has been difficulty in obtaining high resolution structures of the full particle. Here we report a first cryo-EM structure for a hexameric rod composed of human septins 2, 6 and 7 with a global resolution of ~3.6 Å and a local resolution of between ~3.0 Å and ~5.0 Å. By fitting the previously determined high-resolution crystal structures of the component subunits into the cryo-EM map, we are able to provide an essentially complete model for the particle. This exposes SEPT2 NC-interfaces at the termini of the hexamer and leaves internal cavities between the SEPT6-SEPT7 pairs. The floor of the cavity is formed by the two α helices including their polybasic regions. These are locked into place between the two subunits by interactions made with the α and α helices of the neighbouring monomer together with its polyacidic region. The cavity may serve to provide space allowing the subunits to move with respect to one another. The elongated particle shows a tendency to bend at its centre where two copies of SEPT7 form a homodimeric G-interface. Such bending is almost certainly related to the ability of septin filaments to recognize and even induce membrane curvature.

PubMed: 34116125
DOI: 10.1016/j.jmb.2021.167096

Experimental method

ELECTRON MICROSCOPY (3.6 Å)