Structural and thermodynamic characterization of Vibrio fischeri CcdB.
CcdB(Vfi) from Vibrio fischeri is a member of the CcdB family of toxins that poison covalent gyrase-DNA complexes. In solution CcdB(Vfi) is a dimer that unfolds to the corresponding monomeric components in a two-state fashion. In the unfolded state, the monomer retains a partial secondary structure. This observation correlates well with the crystal and NMR structures of the protein, which show a dimer with a hydrophobic core crossing the dimer interface. In contrast to its F plasmid homologue, CcdB(Vfi) possesses a rigid dimer interface, and the apparent relative rotations of the two subunits are due to structural plasticity of the monomer. CcdB(Vfi) shows a number of non-conservative substitutions compared with the F plasmid protein in both the CcdA and the gyrase binding sites. Although variation in the CcdA interaction site likely determines toxin-antitoxin specificity, substitutions in the gyrase-interacting region may have more profound functional implications.
De Jonge
Natalie
N
Structural Biology Brussels, and Department of Molecular and Cellular Interactions, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
Hohlweg
Walter
W
Garcia-Pino
Abel
A
Respondek
Michal
M
Buts
Lieven
L
Haesaerts
Sarah
S
Lah
Jurij
J
Zangger
Klaus
K
Loris
Remy
R
D048908:Aliivibrio fischeri / Q000737:chemistry*; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics; D057927:Hydrophobic and Hydrophilic Interactions; D019906:Nuclear Magnetic Resonance, Biomolecular; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D013816:Thermodynamics
D001427:Bacterial Toxins