Inversion of 3(10)-helix screw sense in a (D-alpha Me)Leu homo-tetrapeptide induced by a guest D-(alpha Me)Val residue.
The terminally blocked tetrapeptide pBrBz-[D-(alpha Me)Leu]2-D-(alpha Me)Val-D-(alpha Me)Leu-OfBu is folded in the crystal state in a left-handed 3(10)-helical structure stabilized by two consecutive 1<--4 C = O...H-N intramolecular H-bonds, as determined by X-ray diffraction analysis. A CD study strongly supports the view that this conformation is also that largely prevailing in MeOH solution. A comparison with the published conformation of pBrBz-[D-(alpha Me)Leu]4-OfBu indicates that incorporation of a single internal beta-branched (alpha Me)Val guest residue into the host homo-tetrapeptide from the gamma-branched (alpha Me)Leu residue is responsible for a dramatic structural perturbation, i.e. an inversion of the 3(10) screw sense from right to left-handed.
Formaggio
F
F
Department of Organic Chemistry, University of Padova, Italy.
Crisma
M
M
Toniolo
C
C
Benedetti
E
E
Di Blasio
B
B
Saviano
M
M
Galdiero
S
S
Kamphuis
J
J
Santini
A
A
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008745:Methylation; D008958:Models, Molecular; D015394:Molecular Structure; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary
C107985:4-bromobenzoyl-(methylleucine)2-methylvaline-methyleucine-tert-butoxy ester; D009842:Oligopeptides