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An example of an amino acid sequence plotted on a helical wheel. Aliphatic residues are shown as blue squares, polar or negatively charged residues as red diamonds, and positively charged residues as black octagons. A helical wheel is a type of plot or visual representation used to illustrate the properties of alpha helices in proteins.
Other examples of four-helix bundles include cytochrome, ferritin, human growth hormone, cytokine, [5] and Lac repressor C-terminal. The four-helix bundle fold has proven an attractive target for de novo protein design, with numerous de novo four-helix bundle proteins having been successfully designed by rational [6] and by combinatorial [7 ...
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.
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 image above contains clickable links This diagram (which is interactive) of protein structure uses PCNA as an example. (Protein secondary structure is the local spatial conformation of the polypeptide backbone excluding the side chains. [1]
The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of local structure, and it is the local structure that is most easily predicted from a sequence of amino acids. The alpha helix has a right-handed helix conformation in which every backbone N−H group hydrogen ...
Helix-loop-helix Consists of alpha helices bound by a looping stretch of amino acids. This motif is seen in transcription factors. Zinc finger Two beta strands with an alpha helix end folded over to bind a zinc ion. Important in DNA binding proteins. Helix-turn-helix
An alpha-helix with hydrogen bonds (yellow dots) The α-helix is the most abundant type of secondary structure in proteins. The α-helix has 3.6 amino acids per turn with an H-bond formed between every fourth residue; the average length is 10 amino acids (3 turns) or 10 Å but varies from 5 to 40 (1.5 to 11 turns). The alignment of the H-bonds ...