Helix packing of leucine-rich peptides: A parallel leucine ladder in the structure of Boc-Aib-Leu-Aib-Aib-Leu-Leu-Leu-Aib-Leu-Aib-OMe

✍ Scribed by Dr. Isabella L. Karle; Judith L. Flippen-Anderson; M. Sukumar; P. Balaram

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 624 KB
• Volume: 12
• Category: Article
• ISSN: 0887-3585
• DOI: 10.1002/prot.340120404

✦ Synopsis

Abstract

The packing of peptide helices in crystals of the leucine‐rich decapeptide Boc‐Aib‐Leu‐Aib‐Aib‐Leu‐Leu‐Leu‐Aib‐Leu‐Aib‐OMe provides an example of ladder‐like leucylleucyl interactions between neighboring molecules. The peptide molecule forms a helix with five 5→1 hydrogen bonds and two 4→1 hydrogen bonds near the C terminus. Three head‐to‐tail NH ċ O = C hydrogen bonds between helices form continuous columns of helices in the crystal. The helicial columns associate in an antiparallel fashion, except for the association of Leu ċ Leu side chains, which occurs along the diagonal of the cell where the peptide helices are parallel. The peptide, with formula C~56~H~102~N~10~O~13~, crystallizes in space group P2~1~2~1~2~1~ with Z = 4 and cell parameters a = 16.774(3) Å, b = 20.032(3) Å and c = 20.117(3) Å; overall agreement factor R = 10.7% for 2014 data with |F~obs~| < 3σ(F); resolution 1.0 Å.