Ligand-induced Dimerization of Middle East Respiratory Syndrome (MERS) Coronavirus nsp5 Protease (3CLpro): IMPLICATIONS FOR nsp5 REGULATION AND THE DEVELOPMENT OF ANTIVIRALS.
J Biol Chem 2015;
290:19403-22. [PMID:
26055715 PMCID:
PMC4528106 DOI:
10.1074/jbc.m115.651463]
[Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Indexed: 12/20/2022] Open
Abstract
All coronaviruses, including the recently emerged Middle East respiratory
syndrome coronavirus (MERS-CoV) from the β-CoV subgroup, require the
proteolytic activity of the nsp5 protease (also known as 3C-like protease,
3CLpro) during virus replication, making it a high value target
for the development of anti-coronavirus therapeutics. Kinetic studies indicate
that in contrast to 3CLpro from other β-CoV 2c members,
including HKU4 and HKU5, MERS-CoV 3CLpro is less efficient at
processing a peptide substrate due to MERS-CoV 3CLpro being a weakly
associated dimer. Conversely, HKU4, HKU5, and SARS-CoV 3CLpro enzymes
are tightly associated dimers. Analytical ultracentrifugation studies support
that MERS-CoV 3CLpro is a weakly associated dimer
(Kd ∼52 μm) with a
slow off-rate. Peptidomimetic inhibitors of MERS-CoV 3CLpro were
synthesized and utilized in analytical ultracentrifugation experiments and
demonstrate that MERS-CoV 3CLpro undergoes significant ligand-induced
dimerization. Kinetic studies also revealed that designed reversible inhibitors
act as activators at a low compound concentration as a result of induced
dimerization. Primary sequence comparisons and x-ray structural analyses of two
MERS-CoV 3CLpro and inhibitor complexes, determined to 1.6 Å, reveal
remarkable structural similarity of the dimer interface with 3CLpro
from HKU4-CoV and HKU5-CoV. Despite this structural similarity, substantial
differences in the dimerization ability suggest that long range interactions by
the nonconserved amino acids distant from the dimer interface may control
MERS-CoV 3CLpro dimerization. Activation of MERS-CoV
3CLpro through ligand-induced dimerization appears to be unique
within the genogroup 2c and may potentially increase the complexity in the
development of MERS-CoV 3CLpro inhibitors as antiviral agents.
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