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X - Possible homology level

H - Homology level

T - Topology level

F - Family level

* - Provisional representative

Keyword search

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

X: jelly-roll
H: Jelly-roll domain in Adenovirus penton base protein
T: Jelly-roll domain in Adenovirus penton base protein
F: Adeno_Penton_B

PF01686

Representatives:

e1x9pA1[A:49-133,A:434-569] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ligands: SO4 ; X-RAY DIFFRACTION 3.3Å

e1x9tA2[A:52-140,A:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; X-RAY DIFFRACTION 3.5Å

e2c9gA2[A:49-140,A:434-570] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9gB2[B:49-140,B:434-570] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9gC2[C:49-140,C:434-570] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9gD2[D:49-140,D:434-570] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9gE2[E:49-140,E:434-570] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9fA2[A:52-140,A:432-567] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9fB2[B:52-140,B:432-567] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9fC2[C:52-140,C:432-567] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9fD2[D:52-140,D:432-567] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2c9fE2[E:52-140,E:432-567] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e2bldA2[A:52-140,A:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB

e2bldB2[B:52-140,B:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB

e2bldC2[C:52-140,C:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB

e2bldD2[D:52-140,D:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB

e2bldE2[E:52-140,E:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB

e2c6sA2[A:49-140,A:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sB2[B:49-140,B:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sC2[C:49-140,C:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sD2[D:49-140,D:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sE2[E:49-140,E:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sF2[F:49-140,F:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sG2[G:49-140,G:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sH2[H:49-140,H:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sI2[I:49-140,I:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sJ2[J:49-140,J:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sK2[K:49-140,K:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sL2[L:49-140,L:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sM2[M:49-140,M:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sN2[N:49-140,N:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e2c6sO2[O:49-140,O:371-507] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

ADENOVIRUS 2,12 PENTON BASE CHIMERA ; X-RAY DIFFRACTION 3.600Å

e3iynM2[M:37-140,M:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH

e3izoA2[A:37-140,A:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e3izoB2[B:37-140,B:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e3izoC2[C:37-140,C:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e3izoD2[D:37-140,D:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e3izoE2[E:37-140,E:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e1vszN2[N:49-140,N:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB

e3zifM1[M:31-134,M:345-480] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e4ar2A2[A:48-140,A:414-542] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

L2 PROTEIN III (PENTON BASE) ; ligands: CA ; X-RAY DIFFRACTION 3.80Å

e4cwuN1[N:52-140,N:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH

e4v4uA2[A:52-140,A:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e4v4uB2[B:52-140,B:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e4v4uC2[C:52-140,C:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e4v4uD2[D:52-140,D:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e4v4uE2[E:52-140,E:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

PENTON PROTEIN ; ELECTRON MICROSCOPY

e6b1tM2[M:37-140,M:434-571] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6cgvN2[N:45-140,N:434-569] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; X-RAY DIFFRACTION 3.8Å

e4aqqA1[A:48-140,A:414-542] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

L2 PROTEIN III (PENTON BASE) ; ligands: CA ; X-RAY DIFFRACTION 4.75Å

e5tx1N1[N:23-127,N:389-519] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton ; ELECTRON MICROSCOPY

e6hcrz1[z:49-140,z:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrA2[A:49-140,A:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrB1[B:49-140,B:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrC2[C:49-140,C:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrD1[D:49-140,D:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrE1[E:49-140,E:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrF1[F:49-140,F:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrG1[G:49-140,G:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrH2[H:49-140,H:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrI1[I:49-140,I:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrJ1[J:49-140,J:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrK2[K:49-140,K:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrL2[L:49-140,L:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrM2[M:49-140,M:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrN2[N:49-140,N:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrO2[O:49-140,O:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrP1[P:49-140,P:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrQ2[Q:49-140,Q:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrR2[R:49-140,R:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrS1[S:49-140,S:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrT1[T:49-140,T:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrV1[V:49-140,V:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrW1[W:49-140,W:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrX1[X:49-140,X:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrY2[Y:49-140,Y:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrZ2[Z:49-140,Z:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcra1[a:49-140,a:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrb2[b:49-140,b:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrc2[c:49-140,c:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrd1[d:49-140,d:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcre2[e:49-140,e:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrf2[f:49-140,f:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrg2[g:49-140,g:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrh1[h:49-140,h:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcri2[i:49-140,i:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrj1[j:49-140,j:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrk1[k:49-140,k:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrl2[l:49-140,l:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrm1[m:49-140,m:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrn1[n:49-140,n:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcro1[o:49-140,o:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrp2[p:49-140,p:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrq1[q:49-140,q:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrr1[r:49-140,r:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrs2[s:49-140,s:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrt1[t:49-140,t:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcru1[u:49-140,u:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrv2[v:49-140,v:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrw2[w:49-140,w:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcrx2[x:49-140,x:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcry1[y:49-140,y:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr12[1:49-140,1:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr22[2:49-140,2:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr31[3:49-140,3:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr41[4:49-140,4:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr52[5:49-140,5:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr61[6:49-140,6:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr72[7:49-140,7:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr81[8:49-140,8:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6hcr92[9:49-140,9:429-557] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6qi5M1[M:1-105,M:312-451] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6z7qA2[A:50-138,A:371-506] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6z7qB1[B:50-138,B:371-506] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6z7qC2[C:50-138,C:371-506] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6z7qD1[D:50-138,D:371-506] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6z7qE2[E:50-138,E:371-506] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6z7nM1[M:33-138,M:378-508] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e6ybaM1[M:35-138,M:371-508] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e7rd1M2[M:51-129,M:395-532] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e7s78N1[N:35-133,N:434-571] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

e7tauN2[N:24-127,N:389-519] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI

Penton protein ; ELECTRON MICROSCOPY

X: Glycosyl hydrolase domain-like

some similarity with Ig fold

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