Select domains for structure alignment

alpha arrays alpha-helix arrays with mainly perpendicular helices

alpha bundles alpha-helix bundles with mainly parallel helices

alpha superhelices repeating alpha-helix hairpins form a superhelix

alpha duplicates or obligate multimers alpha duplicates or monomers associate together to form a compact domain

alpha complex topology alpha domain with complex and unique topology that cannot be described as array or bundle or superhelix

beta barrels single beta-sheet folded upon itself to form a barrel

beta meanders single beta-sheet with mainly meander topology

beta sandwiches two beta-sheets stacked together to form a sandwich

beta duplicates or obligate multimers beta duplicates or monomers associate together to form a compact domain

beta complex topology beta domains with complex and unique topology that cannot be described as barrel or sandwich or meander

a+b two layers one alpha-helix layer and one beta-sheet layer

a+b three layers one mainly antiparallel beta-sheet layer sandwiched between two alpha-helix layers

a+b four layers two beta-sheet layers sandwiched between two alpha-helix layers

a+b complex topology alpha and beta domain with complex and unique topology that cannot be described in layers

a+b duplicates or obligate multimers alpha and beta duplicates or monomers associated together to form a compact domain

a/b barrels repeating beta-alpha units form a barrel

a/b three-layered sandwiches repeating beta-alpha units form a sandwich with a mainly parallel beta-sheet layer stacked between two alpha-helix layers

mixed a+b and a/b alpha and beta domain consists of both a+b and a/b regions

few secondary structure elements stabilized by cofactors or disulfides

extended segments extended, non-globular segments, frequently bind to other proteins to form complexes