Involved in lysis inhibition. Interacts with and inhibits the holin thereby delaying the host cell lysis timing. Lysis inhibition is imposed when a cell infected by a T4-like virus is superinfected by new incoming viruses. This is probably due to the capsid content of the new phage being released in the periplasm because of blockage of entry due to superinfection exclusion. These periplasmically released viral proteins must somehow activate the periplasmic antiholin, which in turn will block the holin multimerization. Interacts (via C-terminus) with holin (via C-terminus); this interaction blocks the holin homomultimerization and delays the host cell lysis. The transmembrane signal-anchor domain can escape spontaneously from the cell inner membrane. It is called SAR for signal-anchor-release for that reason and explains why the antiholin is an extremely instable protein. Superinfection might stabilize it so that it can inhibit holin multimerization and delay lysis. Disulfide bond is required for functionality. Belongs to the T4likevirus antiholin family.