VirJ is a Brucella Virulence Factor Involved in the Secretion of Type IV Secreted Substrates

DEL GIUDICE, MG; DOHMER, PH; JUAN M. SPERA; LAPORTE, T; MARCHESINI, MI; CZIBENER, C; JUAN E. UGALDE

JOURNAL OF BIOLOGICAL CHEMISTRY (ONLINE)

American Society of Biochemistry and Molecular Biology

Lugar: Rockville; Año: 2016

1083-351X

The VirB secretion apparatus in Brucellabelongs to the type IV secretion systems(T4SS) present in many pathogenic bacteriaand is absolutely necessary for the efficientevasion of the Brucella containing vacuole(BCV) from the phagocytic route inprofessional phagocytes. This system isresponsible for the secretion of a plethora ofeffector proteins that alter the biology of thehost cell and promote the intracellularreplication process. Although many VirBsubstrates have been identified in Brucellawe still know very little about the secretionmechanism that mediates their translocationacross the two membranes and theperiplasmic space. In the present manuscriptwe describe the identification of a gene, virJ,which codes for a protein with periplasmiclocalization that is involved in theintracellular replication process andvirulence in mice. Our analysis revealed thatthis protein is necessary for the secretion ofat least two VirB substrates that have aperiplasmic intermediate and that it directlyinteracts with them. We additionally showthat VirJ also associates with the apparatusper se and that its absence affects theassembly of the complex. We hypothesizethat VirJ is part of a secretion platformcomposed of the translocon and severalsecretion substrates and that it probablycoordinates the proper assembly of thismacromolecular complex.