Physicochemical characterization of GBV-C E1 peptides as potential inhibitors of HIV-1 fusion peptide: Interaction with model membranes

Understanding dengue virus capsid protein disordered N-Terminus and pep14-23-based inhibition

Dengue virus (DENV) infection affects millions of people and is becoming a major global disease for which there is no specific available treatment. pep14-23 is a recently designed peptide, based on a conserved segment of DENV capsid (C) protein. It inhibits the interaction of DENV C with host intracellular lipid droplets (LDs), which is crucial for viral replication. Combining bioinformatics and biophysics, here, we analyzed pep14-23 structure and ability to bind different phospholipids, relating that information with the full-length DENV C. We show that pep14-23 acquires α-helical conformation upon binding to negatively charged phospholipid membranes, displaying an asymmetric charge distribution structural arrangement. Structure prediction for the N-terminal segment reveals four viable homodimer orientations that alternatively shield or expose the DENV C hydrophobic pocket. Taken together, these findings suggest a new biological role for the disordered N-terminal region, which may function as an autoinhibitory domain mediating DENV C interaction with its biological targets. The results fit with our current understanding of DENV C and pep14-23 structure and function, paving the way for similar approaches to understanding disordered proteins and improved peptidomimetics drug development strategies against DENV and similar Flavivirus infections.

Surface behavior of peptides from E1 GBV-C protein: Interaction with anionic model membranes and importance in HIV-1 FP inhibition

The interaction between a peptide sequence from GB virus C E1 protein (E1P8) and its structural analogs (E1P8-12), (E1P8-13), and (E1P8-21) with anionic lipid membranes (POPG vesicles and POPG, DPPG or DPPC/DPPG (2:1) monolayers) and their association with HIV-1 fusion peptide (HIV-1 FP) inhibition at the membrane level were studied using biophysical methods. All peptides showed surface activity but leakage experiments in vesicles as well as insertion kinetics in monolayers and lipid/peptide miscibility indicated a low level of interaction: neither E1P8 nor its analogs induced the release of vesicular content and the exclusion pressure values (πe) were clearly lower than the biological membrane pressure (24-30 mN m(-1)) and the HIV-1 FP (35 mN m(-1)). Miscibility was elucidated in terms of the additivity rule and excess free energy of mixing (GE). E1P8, E1P8-12 and E1P8-21 (but not E1P8-13) induced expansion of the POPG monolayer. The mixing process is not thermodynamically favored as the positive GE values indicate. To determine how E1 peptides interfere in the action of HIV-1 FP at the membrane level, mixed monolayers of HIV-1 FP/E1 peptides (2:1) and POPG were obtained. E1P8 and its derivative E1P8-21 showed the greatest HIV-1 FP inhibition. The LC-LE phase lipid behavior was morphologically examined via fluorescence microscopy (FM) and atomic force microscopy (AFM). Images revealed that the E1 peptides modify HIV-1 FP-lipid interaction. This fact may be attributed to a peptide/peptide interaction as indicated by AFM results. Finally, hemolysis assay demonstrated that E1 peptides inhibit HIV-1 FP activity.

Comparison between the behavior of different hydrophobic peptides allowing membrane anchoring of proteins

Membrane binding of proteins such as short chain dehydrogenase reductases or tail-anchored proteins relies on their N- and/or C-terminal hydrophobic transmembrane segment. In this review, we propose guidelines to characterize such hydrophobic peptide segments using spectroscopic and biophysical measurements. The secondary structure content of the C-terminal peptides of retinol dehydrogenase 8, RGS9-1 anchor protein, lecithin retinol acyl transferase, and of the N-terminal peptide of retinol dehydrogenase 11 has been deduced by prediction tools from their primary sequence as well as by using infrared or circular dichroism analyses. Depending on the solvent and the solubilization method, significant structural differences were observed, often involving α-helices. The helical structure of these peptides was found to be consistent with their presumed membrane binding. Langmuir monolayers have been used as membrane models to study lipid-peptide interactions. The values of maximum insertion pressure obtained for all peptides using a monolayer of 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine (DOPE) are larger than the estimated lateral pressure of membranes, thus suggesting that they bind membranes. Polarization modulation infrared reflection absorption spectroscopy has been used to determine the structure and orientation of these peptides in the absence and in the presence of a DOPE monolayer. This lipid induced an increase or a decrease in the organization of the peptide secondary structure. Further measurements are necessary using other lipids to better understand the membrane interactions of these peptides.