A Peptide-Glycolipid Interaction Probed by Retroinverso Peptide Analogues

Cell surface glycolipids are implicated in the formation of lipid rafts and membrane microdomains, where they interact with protein receptors to mediate a variety of cellular processes such as cell-cell recognition, cell adhesion, and membrane signaling. Studies of glycolipid function at the local membrane structures have not been straightforward to date, because the locally clustered structures are labile and their protein binding affinities tend to be weak. While specific glycolipid-binding proteins have been employed as molecular probes for detecting lipid rafts, small peptides may be more suitable for probing glycolipids at the cell surface due to their small size as well as their ease of synthetic preparation and functionalization. Here we report an application of the retroinverso approach as a rapid method to obtain novel glycolipid-binding D-peptide sequences. We have prepared analogues of two known GM1-binding peptides by replacing L-amino acids with D-amino acids, followed by inverting the sequences and characterized their conformational propensity and glycolipid binding properties. Circular dichroism (CD) spectroscopic analysis indicated that all the peptide sequences interacted with GM1 under a micellar condition. We found, by a microplate-based competitive glycolipid binding assay, that one of the retroinverso D-peptide analogues, peptide 3, also binds GM1 as the parent L-peptide 1. These results suggested that in this glycolipid-peptide interaction, the positioning of the side chain functionalities of the peptide is important, while the peptide backbone polarity is not. Glycolipid binding retroinverso D-peptides should be useful for the design of new peptide-based probes for investigating the biological role of cell surface glycolipids.