A Dimerization-Dependent Mechanism Drives the Endoribonuclease Function of Porcine Reproductive and Respiratory Syndrome Virus nsp11.
Bottom Line: The PRRSV nsp11 endoribonuclease plays a vital role in arterivirus replication, but its precise roles and mechanisms of action are poorly understood.Structural and biochemical experiments demonstrated that nsp11 exists mainly as a dimer in solution and that nsp11 may be fully active as a dimer.Mutagenesis and structural analysis revealed NendoU active site residues, which are conserved throughout the order Nidovirales(families Arteriviridae and Coronaviridae) and the major determinants of dimerization (Ser74 and Phe76) in Arteriviridae Importantly, these findings may provide a new structural basis for antiviral drug development.
Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.Show MeSH
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Mentions: In our crystal structure, a total binding surface of 1,309 Å2 is buried at the interface (Fig. 3A), which is smaller than the subunit A-subunit B binding surface of SARS-CoV nsp15, which is 2,253.3 Å2 (Fig. 3C). Regardless, this smaller binding surface may be sufficient to stabilize monomer-monomer interactions because the molecular weight of nsp11 (approximately 25.6) is lower than that of SARS-CoV nsp15 (approximately 38.5). In addition, the catalytic domain of subunit A and the NTD of subunit B are associated with a largely hydrophobic and hydrogen-bonding network (Fig. 2A and B). A total of 16 residues in the NTD of subunit B interact with 17 residues in the catalytic domain of subunit A. Residue Phe76 interacts with residues Tyr150, Leu151, Pro152, Gly164, Val165, and Ser166 via the hydrophobic forces (Fig. 2A and B); thus, Phe76 is a key residue within the dimer interface. Moreover, residue Ser74 interacts with residues Pro152, Val163, and Gly164 and is thus also a key residue within the dimer interface (Fig. 2A and B). In addition, interactional residues Leu77, Val110, and Cys112 were also observed with residue Arg153 (Fig. 2A and B). Therefore, these mutations (S74A, F76A, and R153A) may disturb both hydrophilic and hydrophobic interactions between monomers and prevent the formation of stable dimers.
Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.