title: Crystal structure of L-Pro-L-Leu-Aib-Aib-L-Glu-L-Valol, the C-terminal hexapeptide fragment of trichotoxin.
abstract: The crystal structure of L-prolyl-L-leucyl-alpha-aminoisobutyryl-alpha- aminoiso-butyryl-alpha-L-glutamyl-L-valinol (L-Pro-L-Leu-Aib-Aib-L-Glu-L-Valol), the C-terminal hexapeptide fragment of trichotoxin, has been determined by X-ray crystallography. The hexapeptide forms a right-handed 3(10)-helix consisting of two 10-atom hydrogen-bonded beta-turns of type III and one beta-turn of type I. Two of the intramolecular hydrogen-bonds are particularly weak, thus suggesting that the title compound may adopt non-helical conformations in solution, as observed by circular dichroism. In the crystal the molecules are hydrogen-bonded head-to-tail, forming infinitely long helical columns.
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D002942:Circular Dichroism; D003460:Crystallization; D008958:Models, Molecular; D010446:Peptide Fragments / Q000032:analysis*; D010455:Peptides / Q000032:analysis; D014242:Trichoderma / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D010446:Peptide Fragments; D010455:Peptides; C016161:trichotoxin