The putative cell envelop biogenesis proteins, YciB or IspZ of 179 aas and 5 TMSs, and DcrB or YhhR "phage sensitivity protein" of 185 aas and 1 N-terminal TMS. Both proteins are synergistically required for cell envelope integrity maintenance, and their loss gives rise to abnormal envelopes followed by cell death, possibly due to abnormal retention of porins in the inner membrane (see family description) (Mychack et al. 2019).