title: Synthesis and properties of chemotactic peptide analogs. I. Crystal structure and molecular conformation of HCO-Met-leu-Ain-OMe.
abstract: HCO-Met-Leu-Ain-OMe (2), an analog of the chemotactic peptide HCO-Met-Leu-Phe-OH, containing the conformationally blocked residue of the 2-aminoindane-2-carboxylic acid (Ain) has been synthesized and its crystal and molecular conformation has been determined. Crystals of 2 are monoclinic, space group P2(1), with a = 15.059(7), b = 18.548(7), c = 9.600(4) A; beta = 85.04(3) degrees. The structure has been solved by direct methods and refined to R = 0.069 for 2813 independent reflections with I greater than 2.5 sigma (I). Two independent molecules A and B have been found in the asymmetric unit of the crystal of 2. Their conformation can be described as extended at the Met and Leu residues, but folded at the C-terminal Ain residue. The helical folding is left- and right-handed in the A and B molecule, respectively. The crystal packing is characterized by ribbons of intermolecular hydrogen bonded molecules extended along the c direction. The constrained analog 2 is highly active in the superoxide production, thus indicating that a stabilization of a helical folding at the C-terminal region of chemotactic tripeptides maintains the activity. The orientation of the aromatic ring, with respect to its adjacent backbone atoms, does not seem critical for the activity.
authors.affiliation: Institute of Structural Chemistry, G. Giacomello CNR, Monterotondo Stazione, Rome, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Gavuzzo
authors.forename: G
authors.initials: G
authors.lastname: Lucente
authors.forename: F
authors.initials: F
authors.lastname: Mazza
authors.forename: G P
authors.initials: GP
authors.lastname: Zecchini
authors.forename: M P
authors.initials: MP
authors.lastname: Paradisi
authors.forename: G
authors.initials: G
authors.lastname: Pochetti
authors.forename: I
authors.initials: I
authors.lastname: Torrini
mesh_terms: D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002621:Chemistry; D002630:Chemotactic Factors / Q000138:chemical synthesis / Q000737:chemistry*; D003460:Crystallization; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D002630:Chemotactic Factors; C070748:N-formylmethionyl-leucyl-2-aminoindane-2-carboxylic acid phenylalanine methyl ester; D009240:N-Formylmethionine Leucyl-Phenylalanine