Crystal-state 3D-structural characterization of novel 3(10)-helical peptides.
The crystal-state conformations of two octapeptides, pBrBz-(D-Iva)8-OtBu (8I) and Ac-[L-(alphaMe)Val]8-OH (8II), the heptapeptide Z-[L-(alphaMe)Val]7-OH (7), the hexapeptide Z-[L-(alphaMe)Leu]6-OtBu (6) and the tetrapeptide alkylamide Z-(Aib)2-L-Glu(OMe)-L-Ala-L-Lol (5) were assessed by x-ray diffraction analyses. Two independent molecules are observed in the asymmetric unit of each L-(alphaMe)Val homo-peptide. All four homo-peptides are folded in a regular 3(10)-helical structure (only the C-terminal H-bonded conformation of the D-Iva octapeptide is distorted to a type-I beta-turn). The hydroxyl groups of the C-terminal carboxyl moieties of the two L-(alphaMe)Val homo-peptides participate in an oxy-analogue of the type-III beta-turn conformation. While the two L-(alphaMe)Val 3(10)-helices are right-handed, the D-Iva and L-(alphaMe)Leu helices are left-handed. The tetrapeptide alkylamide is 3(10)-helical at the N-terminus, but it is mixed 3(10)/alpha-helical at the C-terminus.
Crisma
Marco
M
Institute of Biomolecular Chemistry, CNR, Department of Organic Chemistry, University of Padova, Padova, Italy. marco.crisma@unipd.it
Moretto
Alessandro
A
Rainaldi
Mario
M
Formaggio
Fernando
F
Broxterman
Quirinus B
QB
Kaptein
Bernard
B
Toniolo
Claudio
C
D000595:Amino Acid Sequence; D003460:Crystallization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D017433:Protein Structure, Secondary; D014961:X-Ray Diffraction
D010455:Peptides