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
![](/ecod/img/m.gif)
![](/ecod/img/m.gif)
![](/ecod/img/p.gif)
![](/ecod/img/m.gif)
Representatives:
e1xppA1[A:7-105]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
DNA-directed RNA polymerase subunit L ; ligands: ACY,SCN ; X-RAY DIFFRACTION 1.60Å
e1twfK1[K:1-114]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
DNA-DIRECTED RNA POLYMERASE II 13.6 KDA POLYPEPTIDE ; X-RAY DIFFRACTION 2.3Å
e5m3fK1[K:42-142] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases I and III subunit RPAC2 ; ELECTRON MICROSCOPY
e5m3mK1[K:42-142] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases I and III subunit RPAC2 ; ELECTRON MICROSCOPY
e7okxK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7nkxK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerase II subunit RPB11 ; ELECTRON MICROSCOPY
e7okyK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7ol0K1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7eu0K1[K:17-110] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases II, IV and V subunit 11 ; ELECTRON MICROSCOPY
e7eu1K1[K:16-112] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases II, IV and V subunit 11 ; ELECTRON MICROSCOPY
e7fjiK1[K:24-126] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases I and III subunit RPAC2 ; ELECTRON MICROSCOPY
e7fjjK1[K:24-126] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases I and III subunit RPAC2 ; ELECTRON MICROSCOPY
e7ob9K1[K:24-130] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases I and III subunit RPAC2 ; ELECTRON MICROSCOPY
e7obaK1[K:24-130] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases I and III subunit RPAC2 ; ELECTRON MICROSCOPY
e7obbK1[K:24-130] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
DNA-directed RNA polymerases I and III subunit RPAC2 ; ELECTRON MICROSCOPY
e7oo3K1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7oobK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7oopK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7opcK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7opdK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7oznK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7oznW1[W:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7ozoK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7ozoW1[W:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7ozpK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7ozpW1[W:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
e7pksK1[K:1-115] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RNA_pol_L_2 domain-containing protein ; ELECTRON MICROSCOPY
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