The avian infectious bronchitis virus envelope small membrane protein E of 108 aas and 2 TMSs.  IBV E functions as a viroporin and plays a role in virus budding, possibly by altering membrane morphology at the virus assembly site (Pendleton and Machamer 2008). It also mediates ER stress and thereby modulates virion release, apoptosis, viral fitness, and pathogenesis (Li et al. 2019).