Differential protein-protein binding affinities of H-NS family proteins encoded on the chromosome of Pseudomonas putida KT2440 and IncP-7 plasmid pCAR1.

H-NS family proteins encoded on the chromosome of Pseudomonas putida KT2440 (TurA and TurB) and the IncP-7 plasmid pCAR1 (Pmr) commonly have an N-terminal dimerization/oligomerization domain constituted by a central and a terminal dimerization sites. To clarify the dimerization manner at the central dimerization sites of the three homologs, we performed chemical cross-linking analyses with protein variants inactivated at the terminal dimerization site. Comparison of the hetero-dimer ratios among them suggested stronger affinities between the central dimerization sites of TurA and TurB monomers than between TurA and Pmr or TurB and Pmr. Furthermore, analyses of the interaction between truncated TurB containing only a functional terminal dimerization site and full-length proteins suggested that TurB exhibited higher affinities for oligomer complex formation with TurB itself and TurA but not Pmr. Altogether, we revealed stronger interaction between the N-terminal domains of TurA and TurB than between either of them and Pmr.