Forms pores that allow passive diffusion of small molecules across the outer membrane. Homotrimer. Forms mixed heterotrimers with OmpF and with PhoE; other mixed heterotrimers with other porins are also probable. By growth in high osmolarity conditions under control of OmpR (at protein level). No effect on virulence in male BALB/c mice. Belongs to the Gram-negative porin family. Extended N-terminus.