Foldon unfolding mediates the interconversion between M(pro)-C monomer and 3D domain-swapped dimer.

ABSTRACT: The C-terminal domain (M(pro)-C) of SARS-CoV main protease adopts two different fold topologies, a monomer and a 3D domain-swapped dimer. Here, we report that M(pro)-C can reversibly interconvert between these two topological states under physiological conditions. Although the swapped ?(1)-helix is fully buried inside the protein hydrophobic core, the interconversion of M(pro)-C is carried out without the hydrophobic core being exposed to solvent. The 3D domain swapping of M(pro)-C is activated by an order-to-disorder transition of its C-terminal ?(5)-helix foldon. Unfolding of this foldon promotes self-association of M(pro)-C monomers and functions to mediate the 3D domain swapping, without which M(pro)-C can no longer form the domain-swapped dimer. Taken together, we propose that there exists a special dimeric intermediate enabling the protein core to unpack and the ?(1)-helices to swap in a hydrophobic environment, which minimizes the energy cost of the 3D domain-swapping process.

SUBMITTER: Kang X 

PROVIDER: S-EPMC3443179 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature