title: X-ray crystallography and NMR studies of domain-swapped canecystatin-1.
abstract: The three-dimensional structure of canecystatin-1, a potent inhibitor of cysteine proteases from sugarcane (Saccharum officinarum), has been solved in two different crystal forms. In both cases, it is seen to exist as a domain-swapped dimer, the first such observation for a cystatin of plant origin. Size exclusion chromatography and multidimensional NMR spectroscopy show the dimer to be the dominant species in solution, despite the presence of a measurable quantity of monomer undergoing slow exchange. The latter is believed to be the active species, whereas the domain-swapped dimer is presumably inactive, as its first inhibitory loop has been extended to form part of a long β-strand that forms a double-helical coiled coil with its partner from the other monomer. A similar structure is observed in human cystatin C, but the spatial disposition of the two lobes of the dimer is rather different. Dimerization is presumably a mechanism by which canecystatin-1 can be kept inactive within the plant, avoiding the inhibition of endogenous proteases. The structure described here provides a platform for the rational design of specific cysteine protease inhibitors for biotechnological applications.
authors.affiliation: Center for Structural Molecular Biotechnology, Department of Physics and Informatics, Physics Institute of São Carlos, University of São Paulo, São Carlos-SP, Brazil.
authors.forename: Napoleão F
authors.initials: NF
authors.lastname: Valadares
authors.forename: Rodrigo
authors.initials: R
authors.lastname: de Oliveira-Silva
authors.forename: Italo A
authors.initials: IA
authors.lastname: Cavini
authors.forename: Ivo de Almeida
authors.initials: Ide A
authors.lastname: Marques
authors.forename: Humberto D'Muniz
authors.initials: HD
authors.lastname: Pereira
authors.forename: Andrea
authors.initials: A
authors.lastname: Soares-Costa
authors.forename: Flavio
authors.initials: F
authors.lastname: Henrique-Silva
authors.forename: Hans R
authors.initials: HR
authors.lastname: Kalbitzer
authors.forename: Claudia E
authors.initials: CE
authors.lastname: Munte
authors.forename: Richard C
authors.initials: RC
authors.lastname: Garratt
mesh_terms: D018360:Crystallography, X-Ray; D015891:Cystatins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D020125:Mutation, Missense; D019906:Nuclear Magnetic Resonance, Biomolecular; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D031786:Saccharum; D040681:Structural Homology, Protein
chemical_list: D015891:Cystatins; D010940:Plant Proteins; C466627:canecystatin protein, sugarcane