β loop

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A β-loop (also β-turn , English β-turn , more rarely a hairpin loop or hairpin turn ) is a secondary structural motif of peptides and proteins . It occurs more frequently than the similar α-loops , π-loops, or γ-loops .

structure

β-loops consist of four amino acids , whereby a hydrogen bond is formed between the carbonyl function of the first and amino function of the fourth (or the n- and (n + 3) -) amino acid . This type of link is therefore also written as 4 → 1 (corresponding to α-loop: 5 → 1, γ-loop: 3 → 1).

Scheme of β loops (type I and type II)

Subtypes

Depending on the amino acid residues, a distinction is made between β I , β II and β III loops:

  • For steric reasons, the β II type usually (but not always) has the amino acid glycine in the third position.
  • The β III type can be repeated any number of times, in which case a 3 × 10 helix is formed (3.0 amino acids per 360 ° rotation, 10-membered ring of hydrogen bonds). For comparison, the α-helix is a 3.6 13 -helix.

function

The β loop, like the other loops, can be observed when the direction of the amino acid chain changes in the protein structure . It mostly connects β-sheet structures. Often located on the surface of proteins, it participates in the interaction between proteins and other molecules.

See also

literature

  • Jeremy M. Berg, John L. Tymoczko, Lubert Stryer : Biochemistry. 6 edition, Spektrum Akademischer Verlag, Heidelberg 2007. ISBN 978-3-8274-1800-5 .
  • Donald Voet, Judith G. Voet: Biochemistry. 3rd edition, John Wiley & Sons, New York 2004. ISBN 0-471-19350-X .
  • Bruce Alberts , Alexander Johnson, Peter Walter, Julian Lewis, Martin Raff, Keith Roberts: Molecular Biology of the Cell , 5th Edition, Taylor & Francis 2007, ISBN 978-0-8153-4106-2 .

Individual evidence

  1. Thomas Carell , LMU Munich: Lecture script peptides and proteins ( Memento from March 4, 2016 in the Internet Archive ), p. 11, accessed on November 5, 2013.
  2. ^ Saul R. Trevino, Stephanie Schaefer, J. Martin Scholtz, C. Nick Pace (2008): Increasing Protein Conformational Stability by Optimizing β-turn Sequence. Journal of Molecular Biology 373 (1): 211-218. doi : 10.1016 / j.jmb.2007.07.061