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
looks like an elaborated ferredoxin
contains a HTH motif
Representatives:
e2fa1A1[A:84-241] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Probable transcriptional regulator phnF ; X-RAY DIFFRACTION 1.7Å
e2ikkA1[A:86-238] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH
HYPOTHETICAL TRANSCRIPTIONAL REGULATOR YURK ; ligands: SO4 ; X-RAY DIFFRACTION 1.8Å
e2pkhA1[A:109-249] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH
HISTIDINE UTILIZATION REPRESSOR ; ligands: EDO ; X-RAY DIFFRACTION 1.95Å
e3cnvA1[A:98-259] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH
Putative GntR-family transcriptional regulator ; ligands: CL,FLC ; X-RAY DIFFRACTION 2.00Å
e3bwgA2[A:89-233] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH
UNCHARACTERIZED HTH-TYPE TRANSCRIPTIONAL REGULATOR YYDK ; ligands: EDO ; X-RAY DIFFRACTION 2.09Å
e2p19A1[A:2-149] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH
Transcriptional regulator ; X-RAY DIFFRACTION 2.1Å
e2ra5A1[A:66-72,A:103-245] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH
PUTATIVE TRANSCRIPTIONAL REGULATOR ; ligands: IPA,SRT ; X-RAY DIFFRACTION 2.4Å
e2oggA1[A:95-238] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
TREHALOSE OPERON TRANSCRIPTIONAL REPRESSOR ; ligands: GOL,NA,SO4 ; X-RAY DIFFRACTION 2.5Å
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