Crystallization and preliminary crystallographic analysis of the heptad‐repeat complex of SARS coronavirus spike protein

The aetiological agent of an emergent outbreak of atypical pneumonia, severe acute respiratory syndrome (SARS), is a positive‐stranded RNA virus (SARS‐CoV) belonging to the Coronaviridae family with a genome that differs substantially from those of other known coronaviruses. Highly conserved heptad‐repeat (HR1 and HR2) regions in class I viral fusion proteins, including spike protein from SARS coronavirus, interact with each other to form a six‐helix bundle, which is called a fusion core. The crystal structure of the fusion core is expected to greatly facilitate drug design. Crystals of the fusion core of SARS‐CoV spike protein have been grown at 291 K using PEG 4000 as precipitant. The diffraction pattern of the crystal extends to 2.8 Å resolution at 100 K in‐house. The crystals have unit‐cell parameters a = 121.2, b = 66.3, c = 70.0 Å, α = γ = 90, β = 107.4° and belong to space group C 2. Assuming the presence of six molecules per asymmetric unit, the solvent content is estimated to be about 28%.