Part of a cryptic operon that is poorly expressed in vivo. May be an ancestral sugar porin with a broad carbohydrate specificity; it binds aromatic beta-D-glucosides such as arbutin and salicin, but with low affinity compared to the binding of maltooligosaccharides to the LamB porin. Homomonomer; no physical evidence of a homotrimer has been found (PubMed:9426150, PubMed:10027967), however conductance experiments (PubMed:10027967) suggest it may be a homotrimer. The monomer probably consists of 18 antiparallel beta-strands. Can be easily removed from the outer membrane by treatment with detergent. Belongs to the porin LamB (TC 1.B.3) family.