The 3D structure of the fusion primed Sendai F-protein determined by electron cryomicroscopy

The three dimensional (3D) structure of the ectodomain of the entire fusion mediating F protein from Sendai virus [MW (trimer) similar to177 kDa] has been determined by cryoelectron microscopy of single molecules and subsequent 3D reconstruction at a resolution of similar to16 Angstrom. The reconstruction, which has been obtained from the native, proteolytic processed fusion primed F1+F2 form, shows the protein protruding similar to170 Angstrom out of the membrane in a homotrimeric association. It consists of a defined similar to65 Angstrom wide distal head and an adjacent neck, which is connected to an 70 Angstrom elongated stalk. Although the overall shape appears to be similar to the recently reported X-ray structure of the Newcastle disease virus F protein, a closer comparison reveals structural differences suggesting that the investigated Sendai F structure represents an advanced state towards the fusion active conformation.