1.E.8.1.1
Lysis protein, T, of 218 aas and 1 TMS. T holin activity is regulated by the largely periplasmic anti-holin RI (P13304) and the cytoplasmic antiholin R3 (P17309) which act synergistically (Chen and Young 2016). RI is degraded by DegP (Tran et al., 2007).  Mutations in all 3 topological domains if RI (the N-terminal cytoplasmic domain, the single TMS, and the C-terminal periplasmic domain) can abrogate holin function (Moussa et al. 2014).  The short cytoplasmic region of phage T4 holin is essential for the transition from impermeable membrane protein complexes to permeable pores (Schwarzkopf et al. 2025).