Protein found in or associated with the prokaryotic cell outer membrane, a selectively permeable membrane which separates the prokaryotic periplasm from its surroundings. Traditionally only Gram-negative bacteria were thought of as having an outer membrane, but recent work has shown some Actinobacteria, including Mycobacterium tuberculosis, as well as at least 1 archaea (Ignicoccus hospitalis) have a cell outer membrane.

› Cellular component

› cell outer membrane [ GO:0009279 ]