Abstract
Crystals of a 2‐Helix fusion‐core construct of MHV spike protein (commonly referred to as E2) 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. Furthermore, a selenomethionine (SeMet) derivative of MHV spike protein fusion core has been overexpressed and purified. The derivative crystals were obtained under similar conditions and three different wavelength data sets were collected to 2.4 Å resolution from a single derivative crystal at BSRF (Beijing Synchrotron Radiation Facility). The crystals have unit‐cell parameters a = b = 48.3, c = 199.6 Å, α = β = 90, γ = 120° and belong to space group R3. Assuming the presence of two molecules in the asymmetric unit, the solvent content is calculated to be about 46%.
Highlights
Mouse hepatitis virus strain A59 (MHV-A59) belongs to the coronaviruses, which comprise a large and diverse family of enveloped viruses with a single-stranded positive-sense RNA genome of approximately 31 000 bp (Lee et al, 1991; Spaan et al, 1988)
In humans and birds coronaviruses primarily cause upper respiratory tract infections, while porcine and bovine coronaviruses establish enteric infections that result in severe economic loss (Siddell, 1995)
The MHV S protein is cleaved in the Golgi apparatus by a host-cell protease into two sized subunits: the amino-terminal S1 and the carboxyl-terminal S2 (Frana et al, 1985; Luytjes et al, 1987; Sturman et al, 1985)
Summary
Mouse hepatitis virus strain A59 (MHV-A59) belongs to the coronaviruses, which comprise a large and diverse family of enveloped viruses with a single-stranded positive-sense RNA genome of approximately 31 000 bp (Lee et al, 1991; Spaan et al, 1988). Sequence analysis suggests that the coronavirus spike protein has the structural features of a type I membrane protein, including two heptad-repeat regions, a fusion peptide, a transmembrane domain near the carboxyl-terminus of S2 and a hydrophobic signal peptide at the N-terminus of S1 (Spaan et al, 1988). Carboxylterminal to the fusion peptide are two regions containing 4,3 hydrophobic (heptad) repeats, sequence motifs that form a coiled-coil structure. This structure forms a stable protease K-resistant core in the ectodomain of the enveloped glycoprotein (or fusion protein). Heptad-repeat (HR) regions are found in the fusion proteins of many different viruses and form an important characteristic of class I viral fusion proteins (Bosch et al, 2003; Eckert & Kim, 2001). We report the preliminary X-ray crystallographic analysis of the ®rst fusion-core complex of a coronavirus spike protein, namely the MHV fusion core
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