Beta hairpins

Beta hairpins consist of two beta-strands which are antiparallel and hydrogen bonded together (connected by at least one bridge). The hairpins are classified as in Sibanda et al. (1989) using two numbers X:Y, which denote the numer of residues in the loop defined using two different IUPAC conventions. If the end strand residues form two hydrogen bonds, then X=Y. If the distal hydrogen bond is not formed the number of residues in the loop depends on which definition of strand residues is used, according to the IUPAC convention. In practice, if the end hydrogen bond is not formed then Y=X+2.

For the smaller loops the hairpins are dominated by the formation of beta turns (usually I' and II'). The 3:5 hairpins are dominated by one well defined conformation which can be described as a type I turn followed by a G1 bulge. This is called a 3:5 IG hairpin. The most common class among the 4:4 hairpins contains a type I beta turn. Where these particular conformations occur, they are indicated by appropriate letters after the main classification.

If there is a break in the polypeptide chain within the loop region the hairpin will not be classed and the classification will be given as 0:0.


The plots show a schematic diagrams of each hairpin with strand 1 shown as a blue arrow, strand 2 as a green arrow and the loop residues between them in red. The sequences of the two strands and loop are shown in the appropriate colour. Main-chain hydrogen bonds are indicated in purple.

A PostScript or PDF version of the plots (showing 5 hairpins per page) can be generated by clicking on the appropriate icon below the Table.


The table gives the beginning and end residues, and lengths, of the two strands involved in the hairpin togther the with hairpin's class as defined above.


Sibanda BL, Blundell TL and Thornton JM (1989). Conformation of beta-hairpins in protein structures. A systematic classification with applications to modelling by homology, electron density fitting and protein engineering. J. Mol. Biol., 206, 759-777.


Gail Hutchinson 22nd May, 1996 spacer