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Figure 1
Nest situations within polypeptides. Colour scheme: oxygen, red; nitrogen, blue; carbon, grey; chlorine, green. For each peptide, only the main-chain atoms (N, Cα, C and O) are displayed. The N atoms of the nest (three or more) and the atoms hydrogen bonded (or electrostatically attracted) to the nest are shown as spheres. Hydrogen bonds are shown as thin dashed lines. (a) A typical RL nest is illustrated by residues 33–35 of protein 1a2p and bound to its egg, the main-chain carbonyl O atom of residue 30. (bd) YECDUF, HADFAT and POBJAS are short peptides whose nest NH groups are hydrogen bonded to carbonyl groups from adjacent peptides (not shown). YECDUF is an enkephalin analogue. (eg) XESNAK, YIZXIO and NIYXOI mainly consist of α-helices with Schellman loops at their C-termini. (hj) SEGXUX and GORVIS incorporate aspartate resides binding to the nest; these are named Asx-nests. (kps) VEYLEQ, JUJHUR and GIPKAR10 are cyclic peptides incorporating Schellmann loops. JUJHUR and GIPKAR10 are variants of cyclinopeptide A. (m) GUHGIZ is tensin, a cyclic peptide with a compound LRLR nest. Hydrogen bonded within the nest are a main-chain carbonyl group, a serine side chain forming an ST-nest and a water molecule. (n) NUWREC has a nest hydrogen bonded via a type I β-turn and a water molecule. (v) HIYHAY has a nest with a type I′ β-turn and also a bound chloride ion. (q) CUQYUI is a cyclic octapeptide with almost exact dyad symmetry and two nests associated with type I β-turns. (rx) CEWCIQ10 and ZORRED are cyclic peptides, each with a nest associated with a β-turn, the ZORRED nest incorporates a water molecule. (t) NAHTEV consists of a left-handed α-helix followed by a right-handed one. In between the helices is a nest hydrogen bonded to the O atom of ethanol. (w) JOVZAV has a nest associated with a type I β-turn.

Journal logoSTRUCTURAL
BIOLOGY
ISSN: 2059-7983
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