Involved in the transport of maltose and maltodextrins (PubMed:3301537, PubMed:2832377, PubMed:11742115, PubMed:7824948, PubMed:8805519, PubMed:9299337). Indispensable for translocation of maltodextrins (alpha 1-4 linked polyglucosyls) containing more than three glucosyl moieties. A hydrophobic path ('greasy slide') of aromatic residues serves to guide and select the sugars for transport through the channel (PubMed:7824948, PubMed:8805519, PubMed:9299337, PubMed:11742115). Also acts as a receptor for several bacteriophages including lambda (PubMed:4201774). Binds maltosaccharides; when LamB binds starch in soft agar, it inhibits motility (PubMed:2832377). Homotrimer formed of three 18-stranded antiparallel beta-barrels, containing three independent channels (PubMed:1988451, PubMed:16079137, PubMed:7824948, PubMed:8805519, PubMed:9299337) (By similarity). An intrasubunit disulfide bond contributes to trimer stability (PubMed:1988451). By maltose. Resistance to phage lambda (PubMed:4201774). No growth on dextrins (PubMed:2832377). Belongs to the porin LamB (TC 1.B.3) family.