Beta-sandwich
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. 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 consists of a sandwich arrangement of 7-9 antiparallel β-strands arranged in two β-sheets with a beta sheet#Greek [key motif|Greek-key topology]. The Greek-key topology is also found in Human Transthyretin. The jelly [roll fold|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. The L-type lectin domain is a variation of the jelly roll fold. The C2 domain in its typical version is a β-sandwich composed of 8 beta-strands.