A single amino acid change in the transmembrane domain of the VirB8 protein affects dimerization, interaction with VirB10 and Brucella suis virulence

► A variant VirB8 of B. suis with a point mutation G59W in the transmembrane domain has been studied. ► This mutation increases the stability of homodimers of this protein and heterodimers with VirB10. ► This variant is unable to restore the virulence of a virB8 deleted B. suis mutant. ► Similar results are found with the transmembrane variant A55W of A. tumefaciens VirB8. ► Interactions of VirB8 with VirB10 are likely as important as homodimerization of VirB8 for virulence. VirB8 is a critical component of the Brucella suis type IV secretion system (T4SS). We previously showed that the transmembrane (TM) domain plays an essential role in interactions of this protein with itself and the other proteins of the T4SS. We report that a point mutation in this TM domain stabilizes homodimers of VirB8 and heterodimers with VirB10. A similar variant of Agrobacterium tumefaciens VirB8 showed the same phenotype. The B. suis VirB8 variant was unable to complement a virB8 mutant and displayed a dominant negative phenotype when expressed in wild type B. suis. We suggest that interaction of VirB8 with VirB10 could play a major role in the correct function of the B. suis VirB T4SS. AtVirB8physically interacts with AtVirB10 by two hybrid(View interaction) TraJphysically interacts with TraJ by two hybrid (View Interaction 1, 2) AtVirB8physically interacts with AtVirB8 by two hybrid(View interaction) VirB10physically interacts with VirB10 by two hybrid(View interaction) VirB8physically interacts with VirB8 by two hybrid (View Interaction 1, 2) VirB10physically interacts with VirB8 by two hybrid(View interaction) AtVirB10physically interacts with AtVirB10 by two hybrid(View interaction) VirB8physically interacts with VirB10 by two hybrid(View interaction) AtVirB10physically interacts with AtVirB8 by two hybrid(View interaction)