EvpB is a family of Gram-negative probable type VI secretion system components of the tail sheath. They have been known as COG:COG3517. These sheath-components, of which there are many copies in the sheath, are also variously referred to as VipA/VipB and TssB/TssC. On contact with another bacterial cell the sheath contracts and pushes the puncturing device and tube through the cell envelope and punches the target bacterial cell [1].

1: The rise of the Type VI secretion system. Filloux A; F1000Prime Rep. 2013;5:52. PMID:24381728