Description | Viral protein that constitutes the contractile ejection system carried by some tailed prokaryotic viruses such as the Myoviridae. This structure is able to penetrate the host cell envelope, to deliver the viral genome, and possibly some specific proteins, into the cell cytoplasm. A contractile ejection system is composed at least of the contractile sheath, the internal noncontractile tube, the baseplate and the terminator complex. Sheath contraction drives the rigid internal tube through the host cell envelope. Proteins of the ejection apparatus can play an active or a structural role in ejection |