Fiche publication
Date publication
octobre 2019
Journal
PloS one
Auteurs
Membres identifiés du Cancéropôle Est :
Pr LESNIEWSKA Eric
Tous les auteurs :
Garcia-Alles LF, Root K, Maveyraud L, Aubry N, Lesniewska E, Mourey L, Zenobi R, Truan G
Lien Pubmed
Résumé
The carboxysome is a bacterial micro-compartment (BMC) subtype that encapsulates enzymatic activities necessary for carbon fixation. Carboxysome shells are composed of a relatively complex cocktail of proteins, their precise number and identity being species dependent. Shell components can be classified in two structural families, the most abundant class associating as hexamers (BMC-H) that are supposed to be major players for regulating shell permeability. Up to recently, these proteins were proposed to associate as homo-oligomers. Genomic data, however, demonstrated the existence of paralogs coding for multiple shell subunits. Here, we studied cross-association compatibilities among BMC-H CcmK proteins of Synechocystis sp. PCC6803. Co-expression in Escherichia coli proved a consistent formation of hetero-hexamers combining CcmK1 and CcmK2 or, remarkably, CcmK3 and CcmK4 subunits. Unlike CcmK1/K2 hetero-hexamers, the stoichiometry of incorporation of CcmK3 in associations with CcmK4 was low. Cross-interactions implicating other combinations were weak, highlighting a structural segregation of the two groups that could relate to gene organization. Sequence analysis and structural models permitted the localization of interactions that would favor formation of CcmK3/K4 hetero-hexamers. The crystallization of these CcmK3/K4 associations conducted to the elucidation of a structure corresponding to the CcmK4 homo-hexamer. Yet, subunit exchange could not be demonstrated in vitro. Biophysical measurements showed that hetero-hexamers are thermally less stable than homo-hexamers, and impeded in forming larger assemblies. These novel findings are discussed within the context of reported data to propose a functional scenario in which minor CcmK3/K4 incorporation in shells would introduce sufficient local disorder as to allow shell remodeling necessary to adapt rapidly to environmental changes.
Mots clés
Bacterial Proteins, chemistry, Binding Sites, Crystallography, X-Ray, Escherichia coli, genetics, Models, Molecular, Multiprotein Complexes, chemistry, Protein Binding, Protein Engineering, Protein Multimerization, Protein Stability, Synechocystis, genetics, Thermodynamics
Référence
PLoS One. 2019 10 11;14(10):e0223877
