Accumulates harmlessly in the cytoplasmic membrane until it reaches a critical concentration that triggers the formation of nanometer-scale pores (pinholes) causing host cell membrane depolarization and endolysin refolding and release into the periplasmic space (By similarity). Once the pinholin has permeabilized the host cell membrane, the SAR-endolysin is released into the periplasm and breaks down the peptidoglycan layer (By similarity). Determines the precise timing of host cell lysis. Participates with the SAR-endolysin and the U-spanin protein in the sequential events which lead to the programmed host cell lysis releasing the mature viral particles from the host cell (By similarity).