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
X: Subtilisin-like
H: Subtilisin-like
T: Subtilisin-like
F: Peptidase_S8
Representatives:
e1gciA1[A:1-275]
nonrep
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SUBTILISIN ; ligands: CA,GOL,SO4 ; X-RAY DIFFRACTION 0.78Å
e2pwaA1[A:1-279]
nonrep
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PROTEINASE K ; ligands: B2A,CA,NO3,SO4 ; X-RAY DIFFRACTION 0.83Å
e1ga6A1[A:2-370]
nonrep
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SERINE-CARBOXYL PROTEINASE ; ligands: ACT,CA,GOL ; X-RAY DIFFRACTION 1.0Å
e1t1gA1[A:1-357]
nonrep
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kumamolisin ; ligands: CA,SO4 ; X-RAY DIFFRACTION 1.18Å
e1wmdA2[A:1-318]
nonrep
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protease ; ligands: CA,DIO,GOL,SO4 ; X-RAY DIFFRACTION 1.30Å
e1r6vA2[A:105-452]
nonrep
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subtilisin-like serine protease ; ligands: CA ; X-RAY DIFFRACTION 1.7Å
e1v6cA1[A:1-212,A:361-435]
nonrep
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ALKALINE SERINE PROTEASE ; ligands: CA,PMS,SO4 ; X-RAY DIFFRACTION 1.8Å
e3eifA2[A:97-333,A:468-583]
nonrep
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C5a peptidase ; ligands: EPE,NA,SO4 ; X-RAY DIFFRACTION 1.9Å
e2id4A2[A:122-460]
nonrep
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Kexin ; ligands: CA,MLA,NA,NDG ; X-RAY DIFFRACTION 1.900Å
e4zoqM1[M:104-441]
nonrep
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Intracellular serine protease ; X-RAY DIFFRACTION 2.350Å
e4ne9A1[A:153-446]
nonrep
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Proprotein convertase subtilisin/kexin type 9 ; X-RAY DIFFRACTION 2.6Å
e4tr2B2[B:277-614]
nonrep
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Subtilisin-like 1 serine protease ; ligands: CA,PO4 ; X-RAY DIFFRACTION 2.7Å
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