In 1994, a virus emerged in Hendra, Australia, causing respiratory and neurological diseases. It was transmissible from horses to humans, with a mortality rate of 57% in humans and 89% in horses. Since then 2 additional deadly species have emerged in Malaysia and Africa, with evidence of 19 more. The members of this Paramyxoviridae family infect host cells through the fusion protein, F, which is embedded in the viral particle membrane. The bulk of the F protein, the ectodomain, protrudes from the membrane’s surface and undergoes a dramatic refolding to merge the virus and host membranes. At the Advanced Light Source (ALS) Beamline 8.2.2 in the Berkeley Center for Structural Biology, researchers used macromolecular crystallography to study the structure of the Hendra F protein ectodomain in its prefusion form and gain insight into its function. Read the ALS Science Brief.