title: C-terminal domain of SARS-CoV main protease can form a 3D domain-swapped dimer.
abstract: SARS coronavirus main protease (M(pro)) 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. We have reported that both the M(pro) C-terminal domain alone (M(pro)-C) and the N-finger deletion mutant of M(pro) (M(pro)-Delta7) exist as a stable dimer and a stable monomer (Zhong et al., J Virol 2008; 82:4227-4234). Here, we report structures of both M(pro)-C monomer and dimer. The structure of the M(pro)-C monomer is almost identical to that of the C-terminal domain in the crystal structure of M(pro). Interestingly, the M(pro)-C dimer structure is characterized by 3D domain-swapping, in which the first helices of the two protomers are interchanged and each is enwrapped by four other helices from the other protomer. Each folding subunit of the M(pro)-C domain-swapped dimer still has the same general fold as that of the M(pro)-C monomer. This special dimerization elucidates the structural basis for the observation that there is no exchange between monomeric and dimeric forms of M(pro)-C and M(pro)-Delta7.
authors.affiliation: Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing 100871, People' Republic of China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhong
authors.forename: Shengnan
authors.initials: S
authors.lastname: Zhang
authors.forename: Fei
authors.initials: F
authors.lastname: Xue
authors.forename: Xue
authors.initials: X
authors.lastname: Kang
authors.forename: Peng
authors.initials: P
authors.lastname: Zou
authors.forename: Jiaxuan
authors.initials: J
authors.lastname: Chen
authors.forename: Chao
authors.initials: C
authors.lastname: Liang
authors.forename: Zihe
authors.initials: Z
authors.lastname: Rao
authors.forename: Changwen
authors.initials: C
authors.lastname: Jin
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Lou
authors.forename: Bin
authors.initials: B
authors.lastname: Xia