Without its N-finger, the main protease of severe acute respiratory syndrome coronavirus can form a novel dimer through its C-terminal domain.
The main protease (M(pro)) of severe acute respiratory syndrome coronavirus (SARS-CoV) plays an essential role in the extensive proteolytic processing of the viral polyproteins (pp1a and pp1ab), and it is an important target for anti-SARS drug development. It was found that SARS-CoV M(pro) exists in solution as an equilibrium of both monomeric and dimeric forms, and the dimeric form is the enzymatically active form. However, the mechanism of SARS-CoV M(pro) dimerization, especially the roles of its N-terminal seven residues (N-finger) and its unique C-terminal domain in the dimerization, remain unclear. Here we report that the SARS-CoV M(pro) C-terminal domain alone (residues 187 to 306; M(pro)-C) is produced in Escherichia coli in both monomeric and dimeric forms, and no exchange could be observed between them at room temperature. The M(pro)-C dimer has a novel dimerization interface. Meanwhile, the N-finger deletion mutant of SARS-CoV M(pro) also exists as both a stable monomer and a stable dimer, and the dimer is formed through the same C-terminal-domain interaction as that in the M(pro)-C dimer. However, no C-terminal domain-mediated dimerization form can be detected for wild-type SARS-CoV M(pro). Our study results help to clarify previously published controversial claims about the role of the N-finger in SARS-CoV M(pro) dimerization. Apparently, without the N-finger, SARS-CoV M(pro) can no longer retain the active dimer structure; instead, it can form a new type of dimer which is inactive. Therefore, the N-finger of SARS-CoV M(pro) is not only critical for its dimerization but also essential for the enzyme to form the enzymatically active dimer.
Zhong
Nan
N
Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing 100871, P. R. China.
Zhang
Shengnan
S
Zou
Peng
P
Chen
Jiaxuan
J
Kang
Xue
X
Li
Zhe
Z
Liang
Chao
C
Jin
Changwen
C
Xia
Bin
B
D003001:Cloning, Molecular; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics; D010447:Peptide Hydrolases / Q000737:chemistry*; D054730:Protein Interaction Domains and Motifs; D017434:Protein Structure, Tertiary; D011533:Proviruses; D045473:Severe acute respiratory syndrome-related coronavirus / Q000737:chemistry*; D017384:Sequence Deletion
D010447:Peptide Hydrolases