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:
e1ydwA1[A:134-304]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
AX110P-like protein ; X-RAY DIFFRACTION 2.488Å
e1zh8A1[A:132-275]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
OXIDOREDUCTASE ; ligands: EDO,NA,NAP ; X-RAY DIFFRACTION 2.5Å
e3moiA2[A:126-334]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
Probable dehydrogenase ; X-RAY DIFFRACTION 2.5Å
e3e9mA2[A:128-273]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
Oxidoreductase, Gfo/Idh/MocA family ; X-RAY DIFFRACTION 2.7Å
e3e9mC1[C:128-273] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, Gfo/Idh/MocA family ; X-RAY DIFFRACTION 2.7Å
e3e9mB1[B:128-273] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, Gfo/Idh/MocA family ; X-RAY DIFFRACTION 2.7Å
e3e9mD1[D:128-273] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, Gfo/Idh/MocA family ; X-RAY DIFFRACTION 2.7Å
e3ip3A1[A:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; ligands: SO4 ; X-RAY DIFFRACTION 2.14Å
e3ip3B1[B:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; ligands: SO4 ; X-RAY DIFFRACTION 2.14Å
e3ip3C1[C:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; X-RAY DIFFRACTION 2.14Å
e3ip3D2[D:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; X-RAY DIFFRACTION 2.14Å
e3ip3E1[E:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; ligands: SO4 ; X-RAY DIFFRACTION 2.14Å
e3ip3F1[F:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; ligands: SO4 ; X-RAY DIFFRACTION 2.14Å
e3ip3G1[G:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; X-RAY DIFFRACTION 2.14Å
e3ip3H1[H:131-285] Image Pymol Jmol Links: PDB, SCOP, CATH
Oxidoreductase, putative ; X-RAY DIFFRACTION 2.14Å

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