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:
e1u94A1[A:269-328] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RECA PROTEIN ; ligands: CA ; X-RAY DIFFRACTION 1.9Å
e1xp8A1[A:283-341] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
RecA protein ; X-RAY DIFFRACTION 2.50Å
e3cmuA10[A:4270-4333] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein recA ; X-RAY DIFFRACTION 4.200Å
e3cmuA12[A:5270-5328] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein recA ; X-RAY DIFFRACTION 4.200Å
e3cmuA2[A:270-328] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein recA ; X-RAY DIFFRACTION 4.200Å
e3cmuA4[A:1270-1333] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Protein recA ; X-RAY DIFFRACTION 4.200Å
looks like an elaborated ferredoxin
contains a HTH motif
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