Structural Requirements for Molecular Recognition by fMLP Analogs Receptors: Comparative Conformational Analysis of (for-Met-Leu-Phe- OMe) and its Thioamide Analog (for-Met-Leuψ[CSNH]Phe-OMe)

In order to determine the structural requirements of fMLP analogs receptors, this work presents the results of a comparative conformational analysis of the active chemotactic peptide (formyl-Met-Leu-Phe-OMe) and its inactive analog (formyl-Met-Leuψ [CSNH] Phe-OMe) using the theoretical method PEPSEA. This study showed that a γ turn structure centered on the central residue is the native structure of the chemotactic peptide fMLP analogs, where both CO(formyl) and NH(central residue) groups are available and ready to interact with the receptor. The inactive analog fML S P-OMe prefers instead a γ turn structure centered on the Met residue, where the two groups cited above are not available for this interaction. Our results and those of literature enable us to propose the “induced fit” model of Burgen for the molecular recognition process. Consequently, the activity of fMLP analogs chemotactic peptides would not be related to a specific secondary structure (β turn, γ turn or extended….) but rather to the freedom and the availability of the CO(formyl) and the NH group at position 2.