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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). [ 1 ] 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.
Explanation of all-beta topologies: "orthogonal beta-sandwiches" are beta-barrels (as defined in this article); "aligned" beta-sandwiches" correspond to beta-sandwich folds in SCOP classification. all-beta folds in SCOP database (folds 54 to 100 are water-soluble beta-barrels).
This domain has a 3-layer structure, and contains a beta-sandwich fold of unusual topology, and contains a putative tRNA-binding structural motif. [2] In Thermus thermophilus, both the catalytic alpha- and the non-catalytic beta-subunits comprise the characteristic fold of the class II active-site domains.
The Rossmann fold is a tertiary fold found in proteins that bind nucleotides, such as enzyme cofactors FAD, NAD +, and NADP +.This fold is composed of alternating beta strands and alpha helical segments where the beta strands are hydrogen bonded to each other forming an extended beta sheet and the alpha helices surround both faces of the sheet to produce a three-layered sandwich.
The immunoglobulin domain, also known as the immunoglobulin fold, is a type of protein domain that consists of a 2-layer sandwich of 7-9 antiparallel β-strands arranged in two β-sheets with a Greek key topology, [1] [2] consisting of about 125 amino acids. The backbone switches repeatedly between the two β-sheets.
In molecular biology, protein fold classes are broad categories of protein tertiary structure topology. They describe groups of proteins that share similar amino acid and secondary structure proportions.
Two Rossmann folds in Cryptosporidium parvum lactate dehydrogenase, with NAD+ bound. A beta-alpha-beta motif is composed of two beta strands joined by an alpha helix through connecting loops. The beta strands are parallel, and the helix is also almost parallel to the strands. This structure can be seen in almost all proteins with parallel strands.
The fold to which a domain belongs is determined by inspection, rather than by software. The levels of SCOP version 1.75 are as follows. Class: Types of folds, e.g., beta sheets. Fold: The different shapes of domains within a class. Superfamily: The domains in a fold are grouped into superfamilies, which have at least a distant common ancestor.