VirJ is a Brucella virulence factor involved in the secretion of Type IV secreted substrates

MARIELA GISELDA DEL GIUDICE; PETER HANS DOHMER; JUAN MANUEL SPERA; FERNANDO TOMÁS LAPORTE; MARÍA INES MARCHESINI; CECILIA CZIBENER; JUAN E. UGALDE

JOURNAL OF BIOLOGICAL CHEMISTRY (ONLINE)

American Society for Biochemistry and Molecular Biology

Año: 2016

1083-351X

The VirB secretion apparatus in Brucella belongs to the type IV secretion systems (T4SS) present in many pathogenic bacteria and is absolutely necessary for the efficient evasion of the Brucella containing vacuole (BCV) from the phagocytic route in professional phagocytes. This system is responsible for the secretion of a plethora of effector proteins that alter the biology of the host cell and promote the intracellular replication process. Although many VirBsubstrates have been identified in Brucella we still know very little about the secretion mechanism that mediates their translocation across the two membranes and the periplasmic space. In the present manuscript we describe the identification of a gene, virJ, which codes for a protein with periplasmic localization that is involved in the intracellular replication process and virulence in mice. Our analysis revealed that this protein is necessary for the secretion of at least two VirB substrates that have a periplasmic intermediate and that it directly interacts with them. We additionally show that VirJ also associates with the apparatus per se and that its absence affects the assembly of the complex. We hypothesize that VirJ is part of a secretion platform composed of the translocon and several secretion substrates and that it probablycoordinates the proper assembly of this macromolecular complex.