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
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




Representatives:
e1p99A2[A:119-236]
nonrep
Image
Pymol
Jmol Links:
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Hypothetical protein PG110 ; ligands: GLY,MET ; X-RAY DIFFRACTION 1.7Å
e1p99A3[A:40-118,A:237-294]
nonrep
Image
Pymol
Jmol Links:
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CATH, PubMed,
DOI
Hypothetical protein PG110 ; ligands: GLY,MET ; X-RAY DIFFRACTION 1.7Å
e1xs5A2[A:5-86,A:201-244]
nonrep
Image
Pymol
Jmol Links:
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CATH, PubMed,
DOI
Membrane lipoprotein TpN32 ; ligands: MET ; X-RAY DIFFRACTION 1.85Å
e1xs5A3[A:87-200]
nonrep
Image
Pymol
Jmol Links:
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CATH, PubMed,
DOI
Membrane lipoprotein TpN32 ; ligands: MET ; X-RAY DIFFRACTION 1.85Å
e4ef1A1[A:110-227] Image Pymol Jmol Links: PDB, SCOP, CATH
Pheromone cOB1/lipoprotein, YaeC family ; ligands: MSE ; X-RAY DIFFRACTION 1.90Å
e4ef1B2[B:110-227] Image Pymol Jmol Links: PDB, SCOP, CATH
Pheromone cOB1/lipoprotein, YaeC family ; ligands: MSE ; X-RAY DIFFRACTION 1.90Å
e4ef2A1[A:110-227] Image Pymol Jmol Links: PDB, SCOP, CATH
Pheromone cOB1/lipoprotein, YaeC family ; ligands: MSE,PE8 ; X-RAY DIFFRACTION 2.10Å
e4ef2B2[B:110-227] Image Pymol Jmol Links: PDB, SCOP, CATH
Pheromone cOB1/lipoprotein, YaeC family ; ligands: MSE,PEG ; X-RAY DIFFRACTION 2.10Å
e4gotA2[A:112-229] Image Pymol Jmol Links: PDB, SCOP, CATH
Methionine-binding lipoprotein metQ ; ligands: MSE ; X-RAY DIFFRACTION 1.95Å
e3gxaA2[A:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Outer membrane lipoprotein GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.25Å
e3gxaB1[B:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Outer membrane lipoprotein GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.25Å
e3gxaC1[C:121-233] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Outer membrane lipoprotein GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.25Å
e3gxaD2[D:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Outer membrane lipoprotein GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.25Å
e3gxaE2[E:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Outer membrane lipoprotein GNA1946 ; ligands: MET ; X-RAY DIFFRACTION 2.25Å
e3gxaF1[F:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Outer membrane lipoprotein GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.25Å
e4ib2A2[A:117-234] Image Pymol Jmol Links: PDB, SCOP, CATH
Putative Lipoprotein ; ligands: CL,GOL,MET ; X-RAY DIFFRACTION 1.76Å
e4ib2B2[B:117-234] Image Pymol Jmol Links: PDB, SCOP, CATH
Putative Lipoprotein ; ligands: CL,GOL,MET ; X-RAY DIFFRACTION 1.76Å
e3ir1A1[A:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
OUTER MEMBRANE LIPOPROTEIN GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.15Å
e3ir1B2[B:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
OUTER MEMBRANE LIPOPROTEIN GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.15Å
e3ir1C2[C:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
OUTER MEMBRANE LIPOPROTEIN GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.15Å
e3ir1D2[D:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
OUTER MEMBRANE LIPOPROTEIN GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.15Å
e3ir1E2[E:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
OUTER MEMBRANE LIPOPROTEIN GNA1946 ; ligands: MET,SO4 ; X-RAY DIFFRACTION 2.15Å
e3ir1F1[F:124-236] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
OUTER MEMBRANE LIPOPROTEIN GNA1946 ; ligands: MET ; X-RAY DIFFRACTION 2.15Å
e3k2dA1[A:112-225] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
ABC-type metal ion transport system, periplasmic component ; ligands: MET ; X-RAY DIFFRACTION 2.6Å
e3k2dB2[B:112-225] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
ABC-type metal ion transport system, periplasmic component ; ligands: MET ; X-RAY DIFFRACTION 2.6Å
e4k3fA2[A:103-216] Image Pymol Jmol Links: PDB, SCOP, CATH
Probable TonB-dependent receptor ; ligands: GOL,MSE,SO4 ; X-RAY DIFFRACTION 1.60Å
e4ntlA1[A:112-227] Image Pymol Jmol Links: PDB, SCOP, CATH
Lipoprotein, YaeC family ; ligands: ACT,NA,ZN ; X-RAY DIFFRACTION 1.799Å
e3up9A1[A:120-232] Image Pymol Jmol Links: PDB, SCOP, CATH
Putative uncharacterized protein ; ligands: MSE,PE4,PG4 ; X-RAY DIFFRACTION 2.35Å
e4oteA1[A:109-221] Image Pymol Jmol Links: PDB, SCOP, CATH
Lipoprotein ; ligands: ACT,MSE,ZN ; X-RAY DIFFRACTION 2.20Å
e4oteB2[B:109-221] Image Pymol Jmol Links: PDB, SCOP, CATH
Lipoprotein ; ligands: ACT,GOL,MSE ; X-RAY DIFFRACTION 2.20Å
e4qhqA1[A:111-227] Image Pymol Jmol Links: PDB, SCOP, CATH
LIPOPROTEIN ; ligands: MET,PEG ; X-RAY DIFFRACTION 1.4Å

Pseudo group of domains that do not map to PFam family profiles. Domains inside should not be considered as in one family.
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