Article

Domain Swapping Proceeds via Complete Unfolding: A F-19- and H-1-NMR Study of the Cyanovirin-N Protein

Department of Structural Biology, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15261, USA.
Journal of the American Chemical Society (Impact Factor: 11.44). 03/2012; 134(9):4229-35. DOI: 10.1021/ja210118w
Source: PubMed

ABSTRACT Domain swapping creates protein oligomers by exchange of structural units between identical monomers. At present, no unifying molecular mechanism of domain swapping has emerged. Here we used the protein Cyanovirin-N (CV-N) and (19)F-NMR to investigate the process of domain swapping. CV-N is an HIV inactivating protein that can exist as a monomer or a domain-swapped dimer. We measured thermodynamic and kinetic parameters of the conversion process and determined the size of the energy barrier between the two species. The barrier is very large and of similar magnitude to that for equilibrium unfolding of the protein. Therefore, for CV-N, overall unfolding of the polypeptide is required for domain swapping.

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