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:
e4nl4H7[H:631-731] nonrep Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosome assembly protein PriA ; X-RAY DIFFRACTION 2.65Å
e4nl8E4[E:631-731] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosome assembly protein PriA ; X-RAY DIFFRACTION 4.08Å
e4nl8B4[B:631-731] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosome assembly protein PriA ; X-RAY DIFFRACTION 4.08Å
e4nl8A3[A:631-731] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosome assembly protein PriA ; X-RAY DIFFRACTION 4.08Å
e6dgdA5[A:631-730] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosomal protein N' ; ligands: SO4 ; X-RAY DIFFRACTION 3.0Å
e6dcrA5[A:632-731] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosomal protein N' ; ligands: SO4 ; X-RAY DIFFRACTION 1.978Å
e6dcrB2[B:632-730] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosomal protein N' ; X-RAY DIFFRACTION 1.978Å
e6dgdB7[B:631-730] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosomal protein N' ; ligands: SO4 ; X-RAY DIFFRACTION 3.0Å
e8fakH5[H:632-732] Image Pymol Jmol Links: PDB, SCOP, CATH, PubMed, DOI
Primosomal protein N' ; ELECTRON MICROSCOPY
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