Outer membrane protein, bacterial Most of the bacterial outer membrane proteins in this group are porin-like integral membrane proteins (such as ompA) [<cite idref="PUB00006250"/>], but some are small lipid-anchored proteins (such as pal) [<cite idref="PUB00006564"/>]. They are present in the outer membrane of many Gram-negative organisms [<cite idref="PUB00003748"/>]. The C-terminal half of these proteins and is well conserved. The N-terminal half is variable although some of the proteins in this group have the OmpA-like transmembrane domain <db_xref db="INTERPRO" dbkey="IPR000498"/> at the N terminus.