Evolutionary classification of protein domain structures
alpha arraysalpha-helix arrays with mainly perpendicular helices
Representatives:
e1psrA1[A:1-100] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PSORIASIN ; ligands: HO ; X-RAY DIFFRACTION 1.05Å
e1k8uA1[A:2-90] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100A6 ; X-RAY DIFFRACTION 1.15Å
e1xk4A1[A:1-87] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Calgranulin A ; ligands: CA ; X-RAY DIFFRACTION 1.80Å
e1xk4C1[C:4-86] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Calgranulin B ; ligands: CA ; X-RAY DIFFRACTION 1.80Å
e4cfqA1[A:1-87] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.37Å
e4cfqB1[B:1-84] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.37Å
e4cfqD1[D:1-84] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.37Å
e1irjA1[A:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA ; X-RAY DIFFRACTION 2.1Å
e2y5iC1[C:2-99] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100 CALCIUM BINDING PROTEIN Z ; ligands: CA,IPA ; X-RAY DIFFRACTION 2.03Å
e3zwhA1[A:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; ligands: ACT,CA ; X-RAY DIFFRACTION 1.94Å
e3zwhB1[B:-2-90] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; ligands: AZI,CA ; X-RAY DIFFRACTION 1.94Å
e1irjB1[B:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA,CPS ; X-RAY DIFFRACTION 2.1Å
e1irjC1[C:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA ; X-RAY DIFFRACTION 2.1Å
e1irjE1[E:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA,CPS ; X-RAY DIFFRACTION 2.1Å
e1irjF1[F:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA ; X-RAY DIFFRACTION 2.1Å
e1irjG1[G:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA,CPS ; X-RAY DIFFRACTION 2.1Å
e1irjH1[H:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA ; X-RAY DIFFRACTION 2.1Å
e1xk4D1[D:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Calgranulin B ; ligands: CA ; X-RAY DIFFRACTION 1.80Å
e1xk4G1[G:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Calgranulin B ; ligands: CA ; X-RAY DIFFRACTION 1.80Å
e1xk4H1[H:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Calgranulin B ; ligands: CA,FLC ; X-RAY DIFFRACTION 1.80Å
e1xk4K1[K:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Calgranulin B ; ligands: CA ; X-RAY DIFFRACTION 1.80Å
e1xk4L1[L:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Calgranulin B ; ligands: CA,FLC ; X-RAY DIFFRACTION 1.80Å
e1irjD1[D:5-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MIGRATION INHIBITORY FACTOR-RELATED PROTEIN 14 ; ligands: CA,CPS ; X-RAY DIFFRACTION 2.1Å
e2y5iD1[D:2-99] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100 CALCIUM BINDING PROTEIN Z ; ligands: CA,IPA ; X-RAY DIFFRACTION 2.03Å
e2y5iF1[F:2-99] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100 CALCIUM BINDING PROTEIN Z ; ligands: CA,IPA ; X-RAY DIFFRACTION 2.03Å
e2y5iA1[A:3-99] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100 CALCIUM BINDING PROTEIN Z ; ligands: CA,IPA ; X-RAY DIFFRACTION 2.03Å
e2y5iE1[E:2-98] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100 CALCIUM BINDING PROTEIN Z ; ligands: CA,IPA ; X-RAY DIFFRACTION 2.03Å
e2y5iB1[B:3-98] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100 CALCIUM BINDING PROTEIN Z ; ligands: CA,IPA ; X-RAY DIFFRACTION 2.03Å
e4ggfT1[T:1-109] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A9 ; ligands: CA,GOL,MN ; X-RAY DIFFRACTION 1.6Å
e4ggfV1[V:1-109] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A9 ; ligands: CA,GOL,MN,SO4 ; X-RAY DIFFRACTION 1.6Å
e4ggfC1[C:1-108] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A9 ; ligands: CA,GOL,MN ; X-RAY DIFFRACTION 1.6Å
e4cfrA1[A:2-95] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.40Å
e4cfrB1[B:1-100] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.40Å
e1ozoA1[A:1-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S-100P protein ; SOLUTION NMR
e2kaxA1[A:1-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A5 ; SOLUTION NMR
e2lnkB1[B:-11-89] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN S100-A4 ; SOLUTION NMR
e3ko0H1[H:2-95] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0Q1[Q:2-95] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0A1[A:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0B1[B:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0C1[C:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0D1[D:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0F1[F:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0G1[G:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0I1[I:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0J1[J:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0K1[K:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0L1[L:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0O1[O:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0R1[R:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0S1[S:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0T1[T:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3m0wB1[B:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,DIO,P77 ; X-RAY DIFFRACTION 2.800Å
e3m0wH1[H:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,P77 ; X-RAY DIFFRACTION 2.800Å
e3m0wI1[I:2-94] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,P77 ; X-RAY DIFFRACTION 2.800Å
e3ko0E1[E:2-93] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0M1[M:2-93] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0N1[N:2-93] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3ko0P1[P:2-93] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA,TFP ; X-RAY DIFFRACTION 2.3Å
e3m0wJ1[J:2-93] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,DIO,P77 ; X-RAY DIFFRACTION 2.800Å
e1m31A1[A:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Placental calcium-binding protein ; SOLUTION NMR
e1m31B1[B:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Placental calcium-binding protein ; SOLUTION NMR
e2q91A1[A:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100A4 Metastasis Factor ; ligands: CA ; X-RAY DIFFRACTION 1.6300Å
e2q91B1[B:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S100A4 Metastasis Factor ; ligands: CA ; X-RAY DIFFRACTION 1.6300Å
e3c1vA1[A:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.5Å
e3c1vB1[B:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.5Å
e3c1vC1[C:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.5Å
e3c1vD1[D:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.5Å
e3m0wC1[C:3-93] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,DIO,P77 ; X-RAY DIFFRACTION 2.800Å
e4etoA1[A:2-92] Image Pymol Jmol Links: PDB, SCOP, CATH
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.54Å
e3m0wA1[A:2-91] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,DIO,P77 ; X-RAY DIFFRACTION 2.800Å
e3m0wD1[D:3-92] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,P77 ; X-RAY DIFFRACTION 2.800Å
e3m0wE1[E:2-91] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,P77 ; X-RAY DIFFRACTION 2.800Å
e3m0wF1[F:2-91] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,P77 ; X-RAY DIFFRACTION 2.800Å
e3m0wG1[G:2-91] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A4 ; ligands: CA,P77 ; X-RAY DIFFRACTION 2.800Å
e4hszA1[A:3-92] Image Pymol Jmol Links: PDB, SCOP, CATH
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.25Å
e4etoB1[B:1-88] Image Pymol Jmol Links: PDB, SCOP, CATH
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 1.54Å
e3cgaA1[A:4-90] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.030Å
e3cgaB1[B:4-90] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.030Å
e2kaxB1[B:1-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A5 ; SOLUTION NMR
e2kayA1[A:1-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A5 ; ligands: CA ; SOLUTION NMR
e2kayB1[B:1-92] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A5 ; ligands: CA ; SOLUTION NMR
e4dirB1[B:1-87] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A5 ; ligands: CA ; X-RAY DIFFRACTION 2.60Å
e1ozoB1[B:1-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S-100P protein ; SOLUTION NMR
e4dirA2[A:2-87] Image Pymol Jmol Links: PDB, SCOP, CATH
Protein S100-A5 ; ligands: CA ; X-RAY DIFFRACTION 2.60Å
e4hszC2[C:3-92] Image Pymol Jmol Links: PDB, SCOP, CATH
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.25Å
e4hszB2[B:3-92] Image Pymol Jmol Links: PDB, SCOP, CATH
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.25Å
e4hszD2[D:3-92] Image Pymol Jmol Links: PDB, SCOP, CATH
PROTEIN S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.25Å
e2mjwB1[B:1-94] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-P ; SOLUTION NMR
e2mjwD1[D:95-188] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-P ; SOLUTION NMR
e2mrdA1[A:1-101] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; SOLUTION NMR
e2mrdB1[B:1-101] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; SOLUTION NMR
e2rgiB1[B:2-93] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A2 ; ligands: IPA,NA ; X-RAY DIFFRACTION 1.600Å
e4xjkB1[B:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NA ; X-RAY DIFFRACTION 1.760Å
e4xjkD1[D:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NA ; X-RAY DIFFRACTION 1.760Å
e4xjkF1[F:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NA ; X-RAY DIFFRACTION 1.760Å
e4xjkH1[H:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NA ; X-RAY DIFFRACTION 1.760Å
e4xjkJ1[J:4-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NA ; X-RAY DIFFRACTION 1.760Å
e5i8nA1[A:1-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; SOLUTION NMR
e5i8nB1[B:1-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; SOLUTION NMR
e5hydA1[A:2-97] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-Z ; X-RAY DIFFRACTION 2.3Å
e5hydB1[B:2-96] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-Z ; X-RAY DIFFRACTION 2.3Å
e5hydD1[D:2-97] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-Z ; X-RAY DIFFRACTION 2.3Å
e5hydC1[C:2-95] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-Z ; X-RAY DIFFRACTION 2.3Å
e5w1fF1[F:5-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NI ; X-RAY DIFFRACTION 2.60Å
e5lpuD1[D:-1-93] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.1Å
e5lpuC1[C:2-90] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A4 ; ligands: CA ; X-RAY DIFFRACTION 2.1Å
e5w1fB1[B:5-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NA ; X-RAY DIFFRACTION 2.60Å
e5w1fH1[H:5-86] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein S100-A9 ; ligands: CA,NA ; X-RAY DIFFRACTION 2.60Å
e1j55A1[A:1-94] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
S-100P PROTEIN ; ligands: CA ; X-RAY DIFFRACTION 2.0Å
Pseudo group of domains that do not map to PFam family profiles. Domains inside should not be considered as in one family.
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
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