AlphaBeta Loop

Motif Glossary

AlphaBeta Loop

Definition

A motif of five consecutive residues and two H-bonds in which there is:

• H-bond between main-chain CO of residue-1 and main-chain NH of residue-5
• H-bond between main-chain CO of residue-1 and main-chain NH of residue-4

Sub-categories

• 2,3-αRαR (aka: type I or R-handed)
• 2,3-βRαL (aka: type II or R-handed flipped)
• 2,3-αLαL (aka: type I' or L-handed)
• 2,3-βLαR (aka: type II' or L-handed flipped)

Reference

Milner-White, unpublished

Comments

The AlphaBeta Loop replaces the AlphaBeta Motif which, although similar, implicitly restricted the motif to the predominant 2,3-αRαR enantiomer (3D illustration).

Occurrence

The motif (in its predominant 2,3-αRαR conformation) is a common feature of the C- and N-termini of α-helices.

Introduction AlphaBeta Loop Asx Motif Asx Turn Beta Bulge Beta Bulge Loop Beta Link Beta Turn BulgeLoop Motif Crown Bridge Crown Bridge Loop Nest Niche Schellman Loop ST Loop ST Motif ST Staple ST Turn