NMR structure and localization of a large fragment of the SARS-CoV fusion protein: Implications in viral cell fusion

Abstract

The lethal Coronaviruses (CoVs), Severe Acute Respiratory Syndrome-associated Coronavirus (SARS-CoV) and most recently Middle East Respiratory Syndrome Coronavirus, (MERS-CoV) are serious human health hazard. A successful viral infection requires fusion between virus and host cells carried out by the surface spike glycoprotein or S protein of CoV. Current models propose that the S2 subunit of S protein assembled into a hexameric helical bundle exposing hydrophobic fusogenic peptides or fusion peptides (FPs) for membrane insertion. The N-terminus of S2 subunit of SARS-CoV reported to be active in cell fusion whereby FPs have been identified. Atomic-resolution structure of FPs derived either in model membranes or in membrane mimic environment would glean insights toward viral cell fusion mechanism. Here, we have solved 3D structure, dynamics and micelle localization of a 64-residue long fusion peptide or LFP in DPC detergent micelles by NMR methods. Micelle bound structure of LFP is elucidated by the presence of discretely folded helical and intervening loops. The C-terminus region, residues F42-Y62, displays a long hydrophobic helix, whereas the N-terminus is defined by a short amphipathic helix, residues R4-Q12. The intervening residues of LFP assume stretches of loops and helical turns. The N-terminal helix is sustained by close aromatic and aliphatic sidechain packing interactions at the non-polar face. N{H}NOE studies indicated dynamical motion, at ps-ns timescale, of the helices of LFP in DPC micelles. PRE NMR showed that insertion of several regions of LFP into DPC micelle core. Together, the current study provides insights toward fusion mechanism of SARS-CoV.

SARS CoV-2 SPIKE GLYCOPROTEIN MUTATIONS AND CHANGES IN PROTEIN STRUCTURE

“…Clarification of the virus-host interactions will provide significant opportunities not only for the elucidation of the pathogenesis of the disease but also for the development of antiviral drugs (Mahajan et al 2018).…”

Host-membrane interacting interface of the SARS coronavirus envelope protein: Immense functional potential of C-terminal domain

“…The functional aspects of the S protein have been known to mediate receptor binding and virus-cell fusion that occur at either the interface of the plasma membrane or within the endosomal vesicles [ 30 ]. The mechanism of membrane fusion of SARS-CoV-1 mostly belongs to the type I fusion system, where S protein of SARS-CoV-1 comprises of a number of membrane binding regions in the S2 domain identified as fusogenic peptide or FPs by several researchers [ [31] , [32] , [33] ]. Recently Bhattacharjya et al have shown that one of these fusion peptides adopts β-sheet conformation either in the presence of phosphatidylcholine or phosphatidylcholine/cholesterol comprising membrane models with the help of circular dichroism spectroscopy [ 34 ].…”

Mechanistic insights of host cell fusion of SARS-CoV-1 and SARS-CoV-2 from atomic resolution structure and membrane dynamics

“…We have determined 3-D structures of FPs and PTM of SARS-CoV-1 in solution of DPC detergent micelle by NMR methods [ 96 , 97 ]. The atomic resolution structure of the FP ( 770 MYKTPTLKYFGGFNFSQIL 788 ) revealed a bend helical structure presumably resulting from two Gly residues G780 and G781 at the center of the sequence ( Fig.…”

“…Observations of multiple adjacent fusogenic peptides in the S2 domain prompted us to examine structure and membrane localization of a 64-residue long, residues R758-E821, or LFP (long fusion peptide) in detergent micelle solution [ 97 ]. The primary structure of LFP contains FP (residues 770–788) and IFP1 (residues 798–815) with additional residues at the N and C-termini.…”