a b s t r a c tMembrane proteins of the DedA/Tvp38 protein family are involved in membrane integrity and virulence of pathogenic organisms. However, the structure and exact function of any member of this large protein family are still unclear. In the present study we analyzed the functional and structural properties of a DedA homolog. Purified YqjA variants from Escherichia coli are detectable in different oligomeric states and specific homo-interaction of YqjA monomers in the membrane were confirmed by formation of a disulfide bond in the C-terminal transmembrane helix. Moreover, alanine scanning mutagenesis exhibited different interaction sites crucial for YqjA activity vs. dimer formation.