title: Structural characterization of the fusion-active complex of severe acute respiratory syndrome (SARS) coronavirus.
abstract: The causative agent of a recent outbreak of an atypical pneumonia, known as severe acute respiratory syndrome (SARS), has been identified as a coronavirus (CoV) not belonging to any of the previously identified groups. Fusion of coronaviruses with the host cell is mediated by the envelope spike protein. Two regions within the spike protein of SARS-CoV have been identified, showing a high degree of sequence conservation with the other CoV, which are characterized by the presence of heptad repeats (HR1 and HR2). By using synthetic and recombinant peptides corresponding to the HR1 and HR2 regions, we were able to characterize the fusion-active complex formed by this novel CoV by CD, native PAGE, proteolysis protection analysis, and size-exclusion chromatography. HR1 and HR2 of SARS-CoV associate into an antiparallel six-helix bundle, with structural features typical of the other known class I fusion proteins. We have also mapped the specific boundaries of the region, within the longer HR1 domain, making contact with the shorter HR2 domain. Notably, the inner HR1 coiled coil is a stable alpha-helical domain even in the absence of interaction with the HR2 region. Inhibitors binding to HR regions of fusion proteins have been shown to be efficacious against many viruses, notably HIV. Our results may help in the design of anti-SARS therapeutics.
authors.affiliation: Istituto di Ricerche di Biologia Molecolare P. Angeletti, Via Pontina Km 30.600, 00040 Pomezia, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Ingallinella
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bianchi
authors.forename: Marco
authors.initials: M
authors.lastname: Finotto
authors.forename: Giovanna
authors.initials: G
authors.lastname: Cantoni
authors.forename: Debra M
authors.initials: DM
authors.lastname: Eckert
authors.forename: Vinit M
authors.initials: VM
authors.lastname: Supekar
authors.forename: Chiara
authors.initials: C
authors.lastname: Bruckmann
authors.forename: Andrea
authors.initials: A
authors.lastname: Carfi
authors.forename: Antonello
authors.initials: A
authors.lastname: Pessi
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D006801:Humans; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid; D045473:Severe acute respiratory syndrome-related coronavirus / Q000737:chemistry* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D011993:Recombinant Fusion Proteins; D014760:Viral Fusion Proteins