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A polyproline helix is a type of protein secondary structure which occurs in proteins comprising repeating proline residues. [1] A left-handed polyproline II helix (PPII, poly-Pro II, κ-helix [2]) is formed when sequential residues all adopt (φ,ψ) backbone dihedral angles of roughly (-75°, 150°) and have trans isomers of their peptide bonds.
In addition to the protein domains, there are unusual transmembrane elements formed by peptides. A typical example is gramicidin A, a peptide that forms a dimeric transmembrane β-helix. [8] This peptide is secreted by gram-positive bacteria as an antibiotic. A transmembrane polyproline-II helix has not been reported in natural proteins ...
These methods were based on the helix- or sheet-forming propensities of individual amino acids, sometimes coupled with rules for estimating the free energy of forming secondary structure elements. The first widely used techniques to predict protein secondary structure from the amino acid sequence were the Chou–Fasman method [ 17 ] [ 18 ] [ 19 ...
Multiple prolines and/or hydroxyprolines in a row can create a polyproline helix, the predominant secondary structure in collagen. The hydroxylation of proline by prolyl hydroxylase (or other additions of electron-withdrawing substituents such as fluorine ) increases the conformational stability of collagen significantly. [ 20 ]
Polyproline helix; S. Superhelix; T. Tendril perversion; TMPad; Triple helix; X. Xeno nucleic acid This page was last edited on 1 March 2024, at 23:14 (UTC). Text is ...
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Resilin, however, has an absence of an alpha-helix leading to a randomly coiled structure and a disordered structure. [10] This is primarily due to the significantly high proline content in resilin. Proline is a bulky amino acid that has the ability to cause a kink the peptide chain and due to the sterically hindered side chains, it is not able ...