TraB is a homolog of VirB10 which forms part of core complex in Type IV secretion system (T4SS)
This family contains TraB (VirB10 homolog) and a component of the type IV secretion system (T4SS), and similar proteins. T4S system is employed by pathogenic bacteria to export virulence DNAs and/or proteins directly from the bacterial cytoplasm into the host cell. It forms a large multiprotein complex consisting of 12 proteins termed VirB1-11 and VirD4. VirB10, interacts with VirB7 and VirB9, forming the membrane-spanning 'core complex' (CC), around which all other components assemble. The CC is inserted in both the outer and inner membranes, playing a fundamental role as a scaffold for the rest of the T4SS components and actively participating in T4S substrate transfer through the bacterial envelope via conformational changes regulating channel opening and closing. TraB is localized similarly to related proteins in other systems, but unlike in other systems, Neisseria gonorrhoeae TraB does not require the presence of other T4SS components for proper localization. It has been shown to be expressed with TraK (VirB9 homolog) at low levels in wild-type cells, suggesting that gonococcal T4SS may be present in single copy per cell and the small amounts of these proteins are sufficient for DNA secretion.