The N-terminal octapeptide acts as a dimerization inhibitor of SARS coronavirus 3C-like proteinase - Aggregation & Cleavage

The N-terminal octapeptide acts as a dimerization inhibitor of SARS coronavirus 3C-like proteinase
20 January 2006
Ping Wei, Keqiang Fan, Hao Chen, Liang Ma, Changkang Huang, Lei Tan, Dong Xi, Chunmei Li, Ying Liu, Aoneng Cao and Luhua Lai
Biochemical and Biophysical Research Communications
Abstract
The 3C-like proteinase of severe acute respiratory syndrome (SARS) coronavirus has been proposed to be a key target for structural-based drug design against SARS. Accurate determination of the dimer dissociation constant and the role of the N-finger (residues 1?7) will provide more insights into the enzyme catalytic mechanism of SARS 3CL proteinase. The dimer dissociation constant of the wild-type protein was determined to be 14.0 ?M by analytical ultracentrifugation method. The N-finger fragment of the enzyme plays an important role in enzyme dimerization as shown in the crystal structure. Key residues in the N-finger have been studied by site-directed mutagenesis, enzyme assay, and analytical ultracentrifugation. A single mutation of M6A was found to be critical to maintain the dimer structure of the enzyme. The N-terminal octapeptide N8 and its mutants were also synthesized and tested for their potency as dimerization inhibitors. Peptide cleavage assay confirms that peptide N8 is a dimerization inhibitor with a Ki of 2.20 mM. The comparison of the inhibitory activities of N8 and its mutants indicates that the hydrophobic interaction of Met-6 and the electrostatic interaction of Arg-4 contribute most for inhibitor binding. This study describes the first example of inhibitors targeting the dimeric interface of SARS 3CL proteinase, providing a novel strategy for drug design against SARS and other coronaviruses.
Keywords: SARS coronavirus; 3C-like proteinase; Mutational study; N-terminal peptide; Dimerization inhibitor; Peptide inhibitor; Zhang?Poorman plot
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