Unusual conformational preferences of beta-alanine containing cyclic peptides. VII.
In the present paper we describe the synthesis, purification, and single crystal x-ray analysis of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-beta-Ala-beta-Ala). This compound crystallizes in the orthorhombic space group P2I2I2I from methanol and adopts in the solid state an unusual conformation characterized by a cis beta-Ala5-Pro1 peptide bond and by an intramolecular hydrogen bond stabilizing a C11-and a C12-ring structure. The C11 structure contains the Phe3 and the beta-Ala4 at the corner position of the turn; it is the first observation of a type II beta-turn enlargement due to the insertion of an extra methylene group of the beta-alanine residue. The rest of the molecule participates in a newly characterized C12-ring structure, which incorporates a beta-Ala residue at position i of the turn.
Lombardi
A
A
Centro Interdipartimentale di Ricerca su Peptidi Bioattivi, University of Naples Federico II, Italy.
Saviano
M
M
Nastri
F
F
Maglio
O
O
Mazzeo
M
M
Pedone
C
C
Isernia
C
C
Pavone
V
V
D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation; D015091:beta-Alanine / Q000032:analysis*
D010456:Peptides, Cyclic; D015091:beta-Alanine