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15 maj 2024 · What is a stem-loop (hairpin loop)? A Stem-loop can be defined as a hairpin-like pattern formed because of the intramolecular base pairing of the nucleotide sequence (especially in palindromic sequence) within the same molecule.
The structures of commonly occurring loop motifs and β -hairpins are described, with emphasis on their inter-main chain hydrogen bond patterns. Especially new is the realization that β -hairpins occur in four distinct classes that are of evolutionary and structural significance.
A tight or hairpin turn, typically found in globular proteins, is shown in stereo. It contains amino acids 108–112 (ISGNE). The atoms are as in previous drawings: one circle, carbon; two nested circles, oxygen; three nested circles, nitrogen. The dotted line indicates a –C=OH–N– hydrogen bond.
29 lip 2005 · With ubiquitin as a “host” system (see structure), protein engineering methods have been used to determine the energetic contribution of type I′ β-turns to the stability of proteins, with a view to optimizing the rational design of model peptide systems.
16 kwi 2008 · Using naturally occurring peptides as starting points, β-hairpin mimetics have been discovered that possess antimicrobial activity, while others are potent inhibitors of the chemokine receptor CXCR4. β-Hairpin PEMs have also been designed and optimized that mimic an α-helical epitope in p53 and so block its interaction with HDM2.
Buoyed by the strength of the hydrophobic core, other hydrogen bonds, main-chain, guide the b-hairpin into registration by forming a loose network of interactions, making an approximately constant number of hydrogen bonds from a pool of possible candidates.
A hairpin is a special case of a turn, in which the direction of the protein backbone reverses and the flanking secondary structure elements interact. For example, a beta hairpin connects two hydrogen-bonded, antiparallel β-strands.
