Evolutionary classification of protein domain structures
alpha arraysalpha-helix arrays with mainly perpendicular helices
alpha bundlesalpha-helix bundles with mainly parallel helices
alpha superhelicesrepeating alpha-helix hairpins form a superhelix
alpha duplicates or obligate multimersalpha duplicates or monomers associate together to form a compact domain
alpha complex topologyalpha domain with complex and unique topology that cannot be described as array or bundle or superhelix
beta barrelssingle beta-sheet folded upon itself to form a barrel
beta meanderssingle beta-sheet with mainly meander topology
beta sandwichestwo beta-sheets stacked together to form a sandwich
beta duplicates or obligate multimersbeta duplicates or monomers associate together to form a compact domain
beta complex topologybeta domains with complex and unique topology that cannot be described as barrel or sandwich or meander
a+b two layersone alpha-helix layer and one beta-sheet layer




Representatives:
e2bmoA2[A:153-439]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
OXYGENASE-ALPHA NBDO ; ligands: EDO,EOH,FE ; X-RAY DIFFRACTION 1.200Å
e2ckfC1[C:153-216,C:238-446] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RING-HYDROXYLATING DIOXYGENASE ALPHA SUBUNIT ; ligands: FE ; X-RAY DIFFRACTION 1.85Å
e2ckfA3[A:153-452] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RING-HYDROXYLATING DIOXYGENASE ALPHA SUBUNIT ; ligands: FE ; X-RAY DIFFRACTION 1.85Å
e2ckfE1[E:153-218,E:239-453] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RING-HYDROXYLATING DIOXYGENASE ALPHA SUBUNIT ; ligands: FE ; X-RAY DIFFRACTION 1.85Å
e2gbxE1[E:153-454] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Biphenyl 2,3-Dioxygenase Alpha Subunit ; ligands: BNL,FE ; X-RAY DIFFRACTION 2.800Å
e2gbxA3[A:153-454] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Biphenyl 2,3-Dioxygenase Alpha Subunit ; ligands: BNL,FE ; X-RAY DIFFRACTION 2.800Å
e2gbxC1[C:153-451] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Biphenyl 2,3-Dioxygenase Alpha Subunit ; ligands: BNL,FE ; X-RAY DIFFRACTION 2.800Å
e2gbwE2[E:153-454] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Biphenyl 2,3-Dioxygenase Alpha Subunit ; ligands: FE,OXY ; X-RAY DIFFRACTION 1.700Å
e2gbwA3[A:153-454] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Biphenyl 2,3-Dioxygenase Alpha Subunit ; ligands: FE,OXY ; X-RAY DIFFRACTION 1.700Å
e2gbwC1[C:153-451] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Biphenyl 2,3-Dioxygenase Alpha Subunit ; ligands: FE,OXY ; X-RAY DIFFRACTION 1.700Å
e4quqA1[A:155-406] Image Pymol Jmol Links: PDB, SCOP, CATH
Monoxygenase; demethylase ; ligands: AZI,FE ; X-RAY DIFFRACTION 2.25Å
e7q04F3[F:3-39,F:160-247,F:269-411] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Terephthalate 1,2-dioxygenase, terminal oxygenase component subunit alpha 2 ; X-RAY DIFFRACTION 2.281Å
e7q05F2[F:4-39,F:160-247,F:269-413] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Terephthalate 1,2-dioxygenase, terminal oxygenase component subunit alpha 2 ; ligands: FE,SO4,UB7 ; X-RAY DIFFRACTION 2.078Å

Pseudo group of domains that do not map to PFam family profiles. Domains inside should not be considered as in one family.
a+b three layersone mainly antiparallel beta-sheet layer sandwiched between two alpha-helix layers
a+b four layerstwo beta-sheet layers sandwiched between two alpha-helix layers
a+b complex topologyalpha and beta domain with complex and unique topology that cannot be described in layers
a+b duplicates or obligate multimersalpha and beta duplicates or monomers associated together to form a compact domain
a/b barrelsrepeating beta-alpha units form a barrel
a/b three-layered sandwichesrepeating beta-alpha units form a sandwich with a mainly parallel beta-sheet layer stacked between two alpha-helix layers
mixed a+b and a/balpha and beta domain consists of both a+b and a/b regions
few secondary structure elementsstabilized by cofactors or disulfides
extended segmentsextended, non-globular segments, frequently bind to other proteins to form complexes