Dimeric alpha-beta barrel <p>Dimeric alpha-beta barrel domains exhibit an alpha+beta sandwich fold with an antiparallel beta sheet that forms a closed barrel. These domains dimerise through the beta-sheet, and in some cases these dimers may assemble into higher oligomers. Domains with this structure are found in proteins from several different families, including bacterial actinorhodin biosynthesis monooxygenase (ActVa-Orf6), which catalyses the oxidation of an aromatic intermediate of the actinorhodin biosynthetic pathway [<cite idref="PUB00014069"/>]; bacterial muconalactone isomerase, a decamer composed of five dimers [<cite idref="PUB00014070"/>]; and the C-terminal domain of archaeal LprA, a member of the Lrp/AqsnC family of transcription regulators [<cite idref="PUB00014071"/>].</p>