Synthetic formyl tripeptide chemoattractants: a C(alpha,alpha)-dialkylated, amphiphilic glycyl residue at position 1

Structure–activity relationship of for-l-Met l-Leu-l-Phe-OMe analogues in human neutrophils

Neutrophils constitute the first line of defence against bacterial invasion. They migrate to infected tissues along a concentration gradient of chemoattractant molecules, the most important of which is for-Met-Leu-Phe-OH (fMLP). Different responses arise from formylpeptides binding to different isoforms of the specific receptor. The aim of the studies reported herein was to clarify (i) the role of fMLP-OMe amide bonds in receptor-ligand cross-linking, (ii) the nature of the group occupying the N- and C-terminal positions, (iii) the features peculiar to the Met, Leu, and Phe receptor pockets, and (iv) the features which determine the specific neutrophil response.

Chemotactic peptides: fMLF-OMe analogues incorporating proline–methionine chimeras as N-terminal residue

The new fMLF analogues 1-4, incorporating chimeric S-proline-methionine residues (namely the homochiral cis-4(S)-methylthio-(S)-proline (10) and the heterochiral trans-4(R)-methylthio-(S)-proline) (17) in place of the native S-methionine, have been prepared; their solution conformation and activity as agonists or antagonists of formylpeptide receptors have been studied. In addition to peptides 1-4, which maintain the Met gamma-thiomethyl-ether function, the analogues Boc-PLF-OMe (18) and For-PLF-OMe (19) devoid, as compared with 1-4, of position 1 side chain, have been synthesized and their activity examined.

Conformational investigations on analogs of inflammation response inducing chemotactic tripeptide fMLP

Conformations of three analogs of for-L-Met-L-Leu-L-Phe-OH (fMLP), which initiates inflammatory response by interaction with the formyl peptide receptor (FPR), have been investigated by the application of the X-ray crystallographic technique. The investigated analogs of fMLP peptides are as follows: for-L-Met-1-amino-1-cyclooctane-carbonyl(Ac8c)-L-Phe-OMe; for-L-Met-L-Leu-L-p-iodo-Phe-OH; and for-L-Met-di-n-propylglycyl(Dpg)-L-Phe-OMe. The peptide backbone in and is constrained at position of fMLP by the introduction of Calpha,alpha-disubstituted glycines. In peptide, Phe-OMe is substituted by p-iodo-Phe-OH. Crystal structures reveal an overall folded conformation adopted by and. The former is folded in the type II beta-turn, which is stabilized by an intramolecular 1<--4 (formyl) C==O...H--N (Phe) hydrogen bond, whereas the latter is folded in an open turn without any intramolecular hydrogen bond. On the other hand, peptide has an extended conformation, and two different molecules in a crystallographic asymmetric unit form an antiparallel beta-sheet-like structure. In and, residues Ac8c and Dpg adopt left-handed helical and fully extended (C5) conformations, respectively. The cyclooctane ring in Ac8c acquires a boat-chair conformation. Crystal packing of is characterized by the association of aliphatic-aromatic rings via a C--H...pi interaction. In the crystal of, contrary to the usual observations, peptides are interlinked via networks of head-to-tail hydrogen bond and pi...pi interactions, which are generally observed to be mutually exclusive. The structure-function mechanism of the ligand-receptor interaction is discussed.