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:
e1z2uA1[A:1-147]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
Ubiquitin-conjugating enzyme E2 2 ; ligands: BU3,CL,NA,UNX ; X-RAY DIFFRACTION 1.10Å
e2uyzA1[A:3-158]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
SUMO-CONJUGATING ENZYME UBC9 ; ligands: NA ; X-RAY DIFFRACTION 1.400Å
e1jatB1[B:2-137]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
UBIQUITIN-CONJUGATING ENZYME VARIANT MMS2 ; X-RAY DIFFRACTION 1.6Å
e8seaC1[C:2-153] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
; ELECTRON MICROSCOPY
e8sebC1[C:2-153] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
; ELECTRON MICROSCOPY
e8sv8C1[C:2-153] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
; ELECTRON MICROSCOPY
e8wr5A1[A:7-143] Image Pymol Jmol Links: PDB, SCOP, CATH
; ligands: EDO,SO4 ; X-RAY DIFFRACTION 1.70Å
e8tauQ1[Q:29-173] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
; ELECTRON MICROSCOPY
e8gbqA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
; X-RAY DIFFRACTION 1.740Å
e7xedB1[B:0-148] Image Pymol Jmol Links: PDB, SCOP, CATH
; X-RAY DIFFRACTION 2.5Å
e8amsA1[A:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
; ligands: GOL ; X-RAY DIFFRACTION 2.295Å
e8amsB1[B:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
; ligands: GOL ; X-RAY DIFFRACTION 2.295Å
e5eyaA1[A:3-151] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.400Å
e5eyaB1[B:3-151] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.400Å
e5jneB1[B:0-156] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; ligands: 6LN ; X-RAY DIFFRACTION 2.85Å
e5jneF1[F:1-156] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; ligands: 6LN ; X-RAY DIFFRACTION 2.85Å
e1j74A1[A:7-143] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MMS2 ; X-RAY DIFFRACTION 1.9Å
e2c2vL1[L:36-172] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 variant 1 ; X-RAY DIFFRACTION 2.900Å
e2gmiB1[B:3-137] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme variant MMS2 ; X-RAY DIFFRACTION 2.5Å
e1zguA1[A:12-148] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 variant 2 ; SOLUTION NMR
e2a4dA1[A:83-219] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 1 ; X-RAY DIFFRACTION 1.69Å
e1j7dA1[A:7-143] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
MMS2 ; X-RAY DIFFRACTION 1.85Å
e2c2vI1[I:36-172] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 variant 1 ; X-RAY DIFFRACTION 2.900Å
e2c2vC1[C:36-172] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 variant 1 ; X-RAY DIFFRACTION 2.900Å
e2c2vF1[F:36-172] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 variant 1 ; X-RAY DIFFRACTION 2.900Å
e1u9bA1[A:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E9 ; X-RAY DIFFRACTION 2.0Å
e1z5sA1[A:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 I ; X-RAY DIFFRACTION 3.0Å
e2grnA1[A:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 I ; X-RAY DIFFRACTION 1.800Å
e2px9B1[B:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; SOLUTION NMR
e2vrrA1[A:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; ligands: FMT,NA ; X-RAY DIFFRACTION 2.22Å
e1kpsC1[C:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-like protein SUMO-1 conjugating enzyme ; ligands: SO4 ; X-RAY DIFFRACTION 2.50Å
e1kpsA1[A:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-like protein SUMO-1 conjugating enzyme ; X-RAY DIFFRACTION 2.50Å
e1a3sA1[A:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBC9 ; X-RAY DIFFRACTION 2.8Å
e2o25D1[D:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH
SUMO-1-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 2.6Å
e2pe6A1[A:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; X-RAY DIFFRACTION 2.400Å
e1u9aA1[A:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.0Å
e2o25C1[C:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH
SUMO-1-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 2.6Å
e1i7kB1[B:30-175] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 H10 ; X-RAY DIFFRACTION 1.94Å
e2e2cA1[A:30-175] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.0Å
e1q34A1[A:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2-21.5 KDA ; X-RAY DIFFRACTION 2.9Å
e1ayzC1[C:2-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME RAD6 ; X-RAY DIFFRACTION 2.6Å
e1z3dA1[A:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 1 ; X-RAY DIFFRACTION 2.5Å
e1q34B1[B:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2-21.5 KDA ; X-RAY DIFFRACTION 2.9Å
e1ayzB1[B:2-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME RAD6 ; X-RAY DIFFRACTION 2.6Å
e1ayzA1[A:2-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME RAD6 ; X-RAY DIFFRACTION 2.6Å
e1q34C1[C:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2-21.5 KDA ; X-RAY DIFFRACTION 2.9Å
e2aakA1[A:1-150] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed,
UBIQUITIN CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.4Å
e1zdnB1[B:10-156] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2S ; ligands: NA ; X-RAY DIFFRACTION 1.93Å
e1yf9C1[C:13-170] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin carrier protein 4 ; ligands: CL ; X-RAY DIFFRACTION 2.0Å
e1yf9B1[B:13-170] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin carrier protein 4 ; ligands: CL ; X-RAY DIFFRACTION 2.0Å
e2f4wB1[B:12-168] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2, J2 ; X-RAY DIFFRACTION 2.0Å
e1wzvB1[B:2-151] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 L6 ; X-RAY DIFFRACTION 2.1Å
e1fbvC1[C:1004-1147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E12-18 KDA UBCH7 ; ligands: SO4 ; X-RAY DIFFRACTION
e1c4zD1[D:4-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN CONJUGATING ENZYME E2 ; X-RAY DIFFRACTION 2.6Å
e1wzwA1[A:2-151] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin-conjugating enzyme E2 L6 ; X-RAY DIFFRACTION 2.4Å
e2nvuC1[C:27-183] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
NEDD8-conjugating enzyme Ubc12 ; X-RAY DIFFRACTION 2.800Å
e2esoA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 1.50Å
e1jbbA1[A:3-149] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN CONJUGATING ENZYME E2-17.5 KDA ; X-RAY DIFFRACTION 2.0Å
e2o25B2[B:4-154] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2-25 KDA ; X-RAY DIFFRACTION 2.6Å
e1j7dB1[B:3-149] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-17 KDA ; X-RAY DIFFRACTION 1.85Å
e1x23B1[B:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D3 ; X-RAY DIFFRACTION 1.85Å
e2eskA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 1.36Å
e2esqA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 1.44Å
e2c2vH1[H:7-153] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.900Å
e3e46A2[A:4-154] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2-25 kDa ; X-RAY DIFFRACTION 1.86Å
e1y6lB1[B:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2E2 ; X-RAY DIFFRACTION 1.85Å
e2c4oA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB
; ligands: GOL,SO4
e2c4oC1[C:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB
e1fzyB1[B:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-24 KDA ; X-RAY DIFFRACTION 1.9Å
e2fuhA1[A:2-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D3 ; SOLUTION NMR
e1ylaA2[A:4-154] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-25 KDA ; X-RAY DIFFRACTION 2.4Å
e2f4zA1[A:32-192] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
TGTWINSCAN_2721 - E2 DOMAIN ; ligands: GOL ; X-RAY DIFFRACTION 2.11Å
e1fxtA1[A:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-24 KDA ; SOLUTION NMR
e1yh2A1[A:2-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
HSPC150 PROTEIN SIMILAR TO UBIQUITIN-CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.0Å
e2ayvA1[A:1-146] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
ubiquitin-conjugating enzyme E2 ; ligands: UNX ; X-RAY DIFFRACTION 2.00Å
e2clwA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D2 ; ligands: GOL,SO4 ; X-RAY DIFFRACTION 1.940Å
e1x23C1[C:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D3 ; X-RAY DIFFRACTION 1.85Å
e2bf8A1[A:4-154] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-25 KDA ; X-RAY DIFFRACTION 2.3Å
e1w4uA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-17 KDA 2 ; SOLUTION NMR
e2c2vB1[B:7-153] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.900Å
e2clwB1[B:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D2 ; ligands: GOL ; X-RAY DIFFRACTION 1.940Å
e2c2vE1[E:7-153] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.900Å
e1qcqA1[A:2-148] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
PROTEIN (UBIQUITIN CONJUGATING ENZYME) ; X-RAY DIFFRACTION 2.7Å
e2f4zB1[B:33-192] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
TGTWINSCAN_2721 - E2 DOMAIN ; X-RAY DIFFRACTION 2.11Å
e1x23D1[D:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D3 ; X-RAY DIFFRACTION 1.85Å
e2clwD1[D:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D2 ; ligands: GOL ; X-RAY DIFFRACTION 1.940Å
e1x23A1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D3 ; X-RAY DIFFRACTION 1.85Å
e2c4oD1[D:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB
; ligands: GOL
e2clwC1[C:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D2 ; X-RAY DIFFRACTION 1.940Å
e1ylaB2[B:4-154] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-25 KDA ; X-RAY DIFFRACTION 2.4Å
e1y6lA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2E2 ; X-RAY DIFFRACTION 1.85Å
e2c4oB1[B:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB
; ligands: GOL
e3eb6B1[B:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 3.401Å
e2o25A2[A:4-154] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2-25 KDA ; X-RAY DIFFRACTION 2.6Å
e1jbbB1[B:3-149] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN CONJUGATING ENZYME E2-17.5 KDA ; X-RAY DIFFRACTION 2.0Å
e2c2vK1[K:7-153] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.900Å
e1ur6A1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-17 KDA 2 ; SOLUTION NMR; THEORETICAL MODEL
e1tteA2[A:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2-24 kDa ; SOLUTION NMR
e1jatA1[A:3-149] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-17.5 KDA ; X-RAY DIFFRACTION 1.6Å
e2bepA1[A:4-154] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-25 KDA ; ligands: BME ; X-RAY DIFFRACTION 1.8Å
e1fzyA1[A:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-24 KDA ; X-RAY DIFFRACTION 1.9Å
e2gmiA1[A:3-149] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 13 ; X-RAY DIFFRACTION 2.5Å
e2espA1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; ligands: CL,MPD ; X-RAY DIFFRACTION 1.52Å
e1y6lC1[C:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2E2 ; X-RAY DIFFRACTION 1.85Å
e2y9mA1[A:14-179] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-21 KDA ; ligands: EDO ; X-RAY DIFFRACTION 2.60Å
e3ongB1[B:0-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; X-RAY DIFFRACTION 2.3Å
e3rczB1[B:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 1.9Å
e3uinA1[A:2-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 2.6Å
e3a4sA1[A:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 2.7Å
e2kjhA1[A:2-151] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin/ISG15-conjugating enzyme E2 L6 ; SOLUTION NMR
e2klyA1[A:1-165] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 G2 ; SOLUTION NMR
e3oj4A1[A:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D1 ; X-RAY DIFFRACTION 3.4Å
e3hctB1[B:4-151] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.06Å
e3rz3A1[A:6-183] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 R1 ; ligands: U94 ; X-RAY DIFFRACTION 2.3Å
e3l1yA1[A:-4-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D2 ; X-RAY DIFFRACTION 1.6Å
e3tgdA1[A:-4-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D2 ; X-RAY DIFFRACTION 1.8Å
e3k9pA2[A:1-155] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 K ; X-RAY DIFFRACTION 2.8Å
e3fn1B1[B:26-185] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
NEDD8-conjugating enzyme UBE2F ; X-RAY DIFFRACTION 2.5Å
e4epoA1[A:1-144] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB
e3vonB1[B:6-143] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3sqvC1[C:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 L3 ; ligands: GOL ; X-RAY DIFFRACTION 3.3Å
e4ddgB2[B:-1-1029] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2, Ubiquitin thioesterase OTUB1 ; X-RAY DIFFRACTION 3.2987Å
e4ds2A1[A:1-161] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin-conjugating enzyme E2, putative ; X-RAY DIFFRACTION 2.630Å
e4gprA1[A:-1-148] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme family protein ; ligands: CO ; X-RAY DIFFRACTION 1.60Å
e4ap4B1[B:-3-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; X-RAY DIFFRACTION 2.21Å
e4fh1A1[A:3-151] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 13 ; ligands: NHE ; X-RAY DIFFRACTION 2.65Å
e3e95C1[C:21-158] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin-conjugating enzyme E2 ; X-RAY DIFFRACTION 2.500Å
e2ekeA1[A:3-156] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 1.9Å
e2ob4A1[A:9-181] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-32 KDA COMPLEMENTING ; X-RAY DIFFRACTION 2.4Å
e2cyxA1[A:-4-165] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 G2 ; X-RAY DIFFRACTION 2.56Å
e3e95A1[A:2-149] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin carrier protein ; X-RAY DIFFRACTION 2.500Å
e2pwqA1[A:-2-151] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN CONJUGATING ENZYME ; X-RAY DIFFRACTION 1.9Å
e2ediA1[A:1-173] Image Pymol Jmol Links: PDB, SCOP, CATH
NEDD8-conjugating enzyme UBE2F ; SOLUTION NMR
e2c4pA1[A:-2-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; X-RAY DIFFRACTION 2.35Å
e2oxqA1[A:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2D 1 ; X-RAY DIFFRACTION 2.9Å
e2onuA1[A:3-152] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin-conjugating enzyme, putative ; ligands: PG4 ; X-RAY DIFFRACTION 2.38Å
e2h2yA1[A:3-135] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.8Å
e2y4wA1[A:1-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 B ; SOLUTION NMR
e4ii2C1[C:1-149] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 4 ; ligands: SO4 ; X-RAY DIFFRACTION 2.200Å
e4ip3B1[B:2-152] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.3Å
e3w31B1[B:1-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; ligands: IOD ; X-RAY DIFFRACTION 2.96Å
e2grpA1[A:1-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 I ; X-RAY DIFFRACTION 2.050Å
e2groA1[A:1-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 I ; X-RAY DIFFRACTION 1.700Å
e2grqA1[A:1-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 I ; X-RAY DIFFRACTION 1.700Å
e2grrA1[A:1-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 I ; X-RAY DIFFRACTION 1.300Å
e2h2yB1[B:22-134] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.8Å
e2h2yC1[C:22-134] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.8Å
e2h2yD1[D:22-133] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME ; X-RAY DIFFRACTION 2.8Å
e2gjdA1[A:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-18 KDA ; X-RAY DIFFRACTION 1.75Å
e2gjdB1[B:2-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-18 KDA ; X-RAY DIFFRACTION 1.75Å
e2gjdC1[C:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-18 KDA ; X-RAY DIFFRACTION 1.75Å
e2gjdD1[D:3-157] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2-18 KDA ; X-RAY DIFFRACTION 1.75Å
e2c4pB1[B:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; X-RAY DIFFRACTION 2.35Å
e3f92A2[A:-1-155] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 K ; ligands: BME,CA,PG4 ; X-RAY DIFFRACTION 2.23Å
e3hcuB1[B:3-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.60Å
e3hcuD1[D:2-150] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 N ; X-RAY DIFFRACTION 2.60Å
e2ekeB1[B:3-156] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 1.9Å
e3bzhA1[A:46-193] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 E1 ; ligands: GOL ; X-RAY DIFFRACTION 1.6Å
e2q0vA1[A:13-153] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin-conjugating enzyme E2, putative ; ligands: PO4 ; X-RAY DIFFRACTION 2.300Å
e2r0jA1[A:2-148] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin carrier protein ; X-RAY DIFFRACTION 1.850Å
e3e95B1[B:2-149] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin carrier protein ; ligands: UNX ; X-RAY DIFFRACTION 2.500Å
e2oxqB1[B:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2D 1 ; X-RAY DIFFRACTION 2.9Å
e2z5dA1[A:23-174] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 H ; X-RAY DIFFRACTION 2.1Å
e2z5dB1[B:25-175] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 H ; ligands: NA ; X-RAY DIFFRACTION 2.1Å
e3a4sB1[B:0-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 2.7Å
e3l1zA1[A:-4-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D3 ; X-RAY DIFFRACTION 3.17Å
e3a33A1[A:-2-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D2 ; ligands: GOL ; X-RAY DIFFRACTION 2.2Å
e3jvzA1[A:2-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 3.3Å
e3jvzB1[B:2-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 3.3Å
e3jw0A1[A:2-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 3.1Å
e3jw0B1[B:2-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D2 ; X-RAY DIFFRACTION 3.1Å
e3k9oA2[A:3-155] Image Pymol Jmol Links: PDB, SCOP, CATH
Ubiquitin-conjugating enzyme E2 K ; X-RAY DIFFRACTION 1.8Å
e2xwuA1[A:1-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-CONJUGATING ENZYME UBC9 ; X-RAY DIFFRACTION 2.8Å
e3uioA1[A:3-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; X-RAY DIFFRACTION 2.6020Å
e3uipA1[A:2-158] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; X-RAY DIFFRACTION 2.2930Å
e2yb6A1[A:2-151] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 B ; ligands: BME,CL ; X-RAY DIFFRACTION 1.5Å
e2ybfA1[A:3-152] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 B ; ligands: BME,SO4 ; X-RAY DIFFRACTION 2.0Å
e3rz3D1[D:13-93,D:119-183] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 R1 ; ligands: U94 ; X-RAY DIFFRACTION 2.3Å
e3rpgA1[A:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D3 ; X-RAY DIFFRACTION 2.65Å
e3ongD1[D:0-156] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
SUMO-conjugating enzyme UBC9 ; X-RAY DIFFRACTION 2.3Å
e3rz3B1[B:6-183] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 R1 ; ligands: U94 ; X-RAY DIFFRACTION 2.3Å
e3oj4D1[D:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Ubiquitin-conjugating enzyme E2 D1 ; X-RAY DIFFRACTION 3.4Å
e3ptfB1[B:-4-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; X-RAY DIFFRACTION 2.7Å
e2yhoB1[B:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; ligands: ACT ; X-RAY DIFFRACTION 2.1Å
e2yhoD1[D:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; ligands: ZN ; X-RAY DIFFRACTION 2.1Å
e2yhoF1[F:-1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; ligands: ACT,ZN ; X-RAY DIFFRACTION 2.1Å
e2yhoH1[H:1-147] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
UBIQUITIN-CONJUGATING ENZYME E2 D1 ; ligands: ACT ; X-RAY DIFFRACTION 2.1Å
e3o2uA1[A:1025-1188] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
NEDD8-conjugating enzyme UBC12 ; ligands: GOL ; X-RAY DIFFRACTION 2Å
e3vonI1[I:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonh1[h:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonD1[D:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonW1[W:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonP1[P:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vona1[a:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonF1[F:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vono1[o:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonm1[m:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonR1[R:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonM1[M:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e4epoE1[E:-4-134] Image Pymol Jmol Links: PDB, SCOP, CATH Obsolete PDB
e3vond1[d:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonk1[k:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
e3vonY1[Y:6-134] Image Pymol Jmol Links: PDB, SCOP, CATH
UBIQUITIN-CONJUGATING ENZYME E2 VARIANT 2 ; X-RAY DIFFRACTION 3.15Å
Nexte1zuoA1[A:201-362]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
HYPOTHETICAL PROTEIN LOC92912 ; ligands: BME ; X-RAY DIFFRACTION 1.8Å
e2fo3A1[A:9-117]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
Ubiquitin-conjugating enzyme ; X-RAY DIFFRACTION 1.86Å
e1zdnA1[A:6-156]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
UBIQUITIN-CONJUGATING ENZYME E2S ; ligands: NA ; X-RAY DIFFRACTION 1.93Å
e1i7kA1[A:30-175]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
UBIQUITIN-CONJUGATING ENZYME E2 H10 ; X-RAY DIFFRACTION 1.94Å
e1yf9A1[A:13-170]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
Ubiquitin carrier protein 4 ; ligands: CL ; X-RAY DIFFRACTION 2.0Å
e2f4wA1[A:12-168]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
UBIQUITIN-CONJUGATING ENZYME E2, J2 ; X-RAY DIFFRACTION 2.0Å
e3cegA1[A:4493-4790]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
BACULOVIRAL IAP REPEAT-CONTAINING PROTEIN 6 ; X-RAY DIFFRACTION 2.01Å
e1wzvA1[A:2-151]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH
UBIQUITIN-CONJUGATING ENZYME E2 L6 ; X-RAY DIFFRACTION 2.1Å
e2awfA1[A:7-131]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
UBIQUITIN-CONJUGATING ENZYME E2 G1 ; X-RAY DIFFRACTION 2.1Å
e1yrvA1[A:1-148]
nonrep
Image
Pymol
Jmol Links:
PDB,
SCOP,
CATH, PubMed,
DOI
ubiquitin-conjugating ligase MGC351130 ; X-RAY DIFFRACTION 2.181Å

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