Pycsar (pyrimidine cyclase system for antiphage resistance) provides immunity against bacteriophage. The pyrimidine cyclase (PycC) synthesizes cyclic nucleotides in response to infection; these serve as specific second messenger signals. The signals activate the adjacent effector, leading to bacterial cell death and abortive phage infection. A clade E Pycsar system. The effector component of a two-gene Pycsar system. Expression of this and adjacent cytidylate cyclase Ec303145PycC (AC P0DV26) confers resistance to bacteriophage P1, T5, lambda-vir and phi27 (PubMed:34644530). Probably only responds to cCMP (produced by its cognate NTP cyclase), acts by impairing membrane integrity (Probable).