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

The VirB secretion apparatus in Brucella belongs to the type IV secretion systems present in many pathogenic bacteria and is absolutely necessary for the efficient evasion of the Brucella-containing vacuole 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 VirB substrates 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.