Beta-sandwich
{{Short description|Two opposing antiparallel beta sheets that commonly occur in proteins}}
Image:Protein TNC PDB 1ten.png (PDB entry: {{PDB2|1TEN}}).]]
Beta-sandwich or β-sandwich domains consisting of 80 to 350 amino acids occur commonly in proteins. They are characterized by two opposing antiparallel beta sheets (β-sheets).{{cite journal|last1=Kister|first1=A. E.|last2=Fokas|first2=A. S.|last3=Papatheodorou|first3=T. S.|last4=Gelfand|first4=I. M.|title=Strict rules determine arrangements of strands in sandwich proteins |journal=PNAS| date=2006| volume=103| issue=11| pages=4107–4110| doi=10.1073/pnas.0510747103| pmid=16537492| pmc=1449654|bibcode=2006PNAS..103.4107K|doi-access=free}} The number of strands found in such domains may differ from one protein to another. β-sandwich domains are subdivided in a variety of different folds. The immunoglobulin-type fold found in antibodies (Ig-fold) consists of a sandwich arrangement of 7-9 antiparallel β-strands arranged in two β-sheets with a Greek-key topology.{{Citation|last1=Bokhove|first1=Marcel|title=Chapter Thirteen - Structure of Zona Pellucida Module Proteins|date=2018-01-01|url=http://www.sciencedirect.com/science/article/pii/S0070215318300395|journal=Current Topics in Developmental Biology|volume=130|pages=413–442|editor-last=Litscher|editor-first=Eveline S.|series=Extracellular Matrix and Egg Coats|publisher=Academic Press|language=en|doi=10.1016/bs.ctdb.2018.02.007|access-date=2020-12-15|last2=Jovine|first2=Luca|pmid=29853186|editor2-last=Wassarman|editor2-first=Paul M.|editor2-link= Paul M Wassarman|url-access=subscription}} The Greek-key topology is also found in Human Transthyretin. The jelly-roll topology is found in carbohydrate binding proteins such as concanavalin A and various lectins, in the collagen binding domain of Staphylococcus aureus Adhesin and in modules that bind fibronectin as found in Tenascin (Third Fibronectin Type III Repeat). The L-type lectin domain is a variation of the jelly roll fold. The C2 domain in its typical version (PKC-C2) is a β-sandwich composed of 8 beta-strands (β-strands).
References
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