Editing Beta sheet (section)

===β-α-β motif===
Due to the chirality of their component amino acids, all strands exhibit right-handed twist evident in most higher-order β-sheet structures. In particular, the linking loop between two parallel strands almost always has a right-handed crossover chirality, which is strongly favored by the inherent twist of the sheet.<ref>See sections II B and III C, D in {{cite book | vauthors = Richardson JS |year= 1981 |title=Anatomy and Taxonomy of Protein Structures |chapter= The Anatomy and Taxonomy of Protein Structure |journal=Advances in Protein Chemistry |volume=34 |pages=167–339|isbn=0-12-034234-0 |doi=10.1016/s0065-3233(08)60520-3|pmid= 7020376 }}</ref> This linking loop frequently contains a helical region, in which case it is called a [[beta-alpha-beta|β-α-β]] motif. A closely related motif called a β-α-β-α motif forms the basic component of the most commonly observed protein [[tertiary structure]], the [[TIM barrel]].

[[File:beta-meander1.png|left|thumb|300px| The β-meander motif from Outer surface protein A (OspA).<ref name=":0">{{cite journal | vauthors = Makabe K, McElheny D, Tereshko V, Hilyard A, Gawlak G, Yan S, Koide A, Koide S | display-authors = 6 | title = Atomic structures of peptide self-assembly mimics | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 47 | pages = 17753–8 | date = November 2006 | pmid = 17093048 | pmc = 1693819 | doi = 10.1073/pnas.0606690103 | bibcode = 2006PNAS..10317753M | doi-access = free }}</ref>  The image above shows a variant of OspA (OspA+3bh) that contains a central, extended β-meander β-sheet featuring three additional copies (in red) of the core OspA β-hairpin (in grey) that have been duplicated and reinserted into the parent OspA β-sheet.]]
[[File:5CPAgood.png|right|thumb|Psi-loop motif from [[Carboxypeptidase A]]]]