Core component of the type VI (T6SS) secretion system that plays a role in the release of toxins targeting both eukaryotic and prokaryotic species. Plays an essential role in stabilization of assembled TssK1 structure at a fixed perimembrane site. In the deletion mutant, TssB1 is still recruited to the structure containing TssK1, but the assembly of TssB1-sheath is aborted likely at the nucleation stage.