title: SARS-coronavirus spike S2 domain flanked by cysteine residues C822 and C833 is important for activation of membrane fusion.
abstract: The S2 domain of the coronavirus spike (S) protein is known to be responsible for mediating membrane fusion. In addition to a well-recognized cleavage site at the S1-S2 boundary, a second proteolytic cleavage site has been identified in the severe acute respiratory syndrome coronavirus (SARS-CoV) S2 domain (R797). C-terminal to this S2 cleavage site is a conserved region flanked by cysteine residues C822 and C833. Here, we investigated the importance of this well conserved region for SARS-CoV S-mediated fusion activation. We show that the residues between C822-C833 are well conserved across all coronaviruses. Mutagenic analysis of SARS-CoV S, combined with cell-cell fusion and pseudotyped virion infectivity assays, showed a critical role for the core-conserved residues C822, D830, L831, and C833. Based on available predictive models, we propose that the conserved domain flanked by cysteines 822 and 833 forms a loop structure that interacts with components of the SARS-CoV S trimer to control the activation of membrane fusion.
authors.affiliation: C4127 Veterinary Medical Center, Department of Microbiology and Immunology, Cornell University, Ithaca NY 14853, USA.
authors.forename: Ikenna G
authors.initials: IG
authors.lastname: Madu
authors.forename: Sandrine
authors.initials: S
authors.lastname: Belouzard
authors.forename: Gary R
authors.initials: GR
authors.lastname: Whittaker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002459:Cell Fusion; D002460:Cell Line; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D006224:Cricetinae; D003545:Cysteine / Q000235:genetics*; D006801:Humans; D008561:Membrane Fusion; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics* / Q000502:physiology; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000235:genetics*
chemical_list: D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus; D003545:Cysteine