Porin Omp2B of 362 aas.  Allows facilitated diffusion of solutes through the porin (Vassen et al. 2019). Among surface protein antigens, the Omp2a and Omp2b porins display the highest diversity in Brucella species. The genes coding for these proteins are closely linked in the Brucella genome and oriented in opposite directions. They share between 85 and 100% sequence identity depending on the Brucella species, biovar, or genotype. Only the omp2b gene copy has been shown to be expressed, and genetic variation is extensively generated by gene conversion between the two copies. Size reduction occurred affecting the region encoding the surface L5 loop of the porin, previously shown to be critical in sugar permeability, followed by a nucleotide reduction in the surface L8 loop-encoding region. It resulted in a final omp2b gene size shared between two distinct clades of non-classical Brucella spp. (African bullfrog isolates) and the group of classical Brucella species (Leclercq et al. 2019).