Glycosylated β-Endorphin Analogue Peptides Adopt Variable Amphipathic Conformations in the Presence of Lipid Bilayers

A series of glycosylated b-endorphin analogues designed to understand how the combining C-terminal amphipathic helical address segments, charge effect on the address segments and variable linker segments promote the blood-brain barrier (BBB) with the generalized structure Tyr-d-Thr-Gly-Phe-Leu-Pro-Asn-Leu- Aib-Glu-Lys-Aib-Leu-Lys-Ser[O-Glucose]-Leu-CONH_2, have been synthesized and tested using human receptors expressed in CHO cells. These peptides have been studied by circular dichroism and by 2D-NMR in the presence of water; SDS micelles. In water, the glycosylated analogues showed only nascent helix behavior and random coil conformations. Chemical shift indices and Nuclear Overhauser Effects (NOE) confirmed helical structures in the presence of membrane mimics. Detailed backbone conformations were calculated through distance constraints provide by NOE volumes. Based on the CD experiment, most of glycosylated b-endorphin analogues were largely helical in the presence of membrane bilayer models and several of them showed less helical and random coil structure in SDS micelles. These designed peptides with variable amphipathicities showed effective glycopeptides penetration through BBB, and were pan-agonists, showing low nanomolar binding at the μ, δ and κ-opioid receptors.  

Acknowledgement:

We thank the Office of Naval Research (N00014-05-1-0807 & N00014-02-1-0471), the National Science Foundation (CHE-607917) and National Institute of Neurological Disorders and Stroke #R01NS52727