actively participates in molecular entity molecular entity translocation of RicA into macrophage Brucella type IV secretion system T4SS, Brucella In Brucella, the VirB T4SS permits the injection of bacterial effectors inside host cells, leading to subversion of signaling pathways and favoring bacterial growth and pathogenesis. The virB operon promoter is tightly regulated by a combination of transcriptional activators and repressors that are expressed according to the environmental conditions encountered by Brucella. Recent advances have shed light on the Brucella T4SS regulatory mechanisms and also its substrates. Characterization of the targets and functions of these translocated effectors is underway and will help understand the role of the T4SS in the establishment of a replication niche inside host cells. [Brucella T4SS: the VIP pass inside host cells. Lacerda TL, Salcedo SP, Gorvel JP. Curr Opin Microbiol. 2013 Feb;16(1):45-51. doi: 10.1016/j.mib.2012.11.005. Epub 2013 Jan 11. Review. PMID: 23318140] Brucella T4SS The Brucella T4SS is composed of 11 Brucella virB proteins.