pH-Dependent Conformational Changes and Topology of a Herpesvirus Translocating Peptide in a Membrane-Mimetic Environment

Abstract

Pol peptide, an oligopeptide corresponding to the 27 C-terminal amino acids of DNA polymerase from herpes simplex virus type 1, has recently been suggested to translocate from endosomal compartments into the cytosol after being intracellularly delivered via a protein carrier. While an acidic environment was thought to be important for Pol peptide membrane translocation, the mechanism of translocation remains unclear. To investigate the influence of an acidic environment on the conformational properties of the peptide and on its propensity to interact with lipid bilayers, we characterized the structure of Pol peptide at different pH values by both circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy. The influence of detergent micelles, which mimic biological lipid membranes, on the peptide secondary structure was also studied. Our CD results indicate that the peptide is in a random conformation in aqueous solution at both acidic and basic pH, whereas in the presence of dodecylphosphocholine (DPC) micelles, it assumes a partial alpha-helical structure which is significantly pH-dependent. An NMR study confirmed that, in the presence of DPC micelles, a short C-terminal alpha-helix is present at pH 6.5, whereas almost two-thirds of the peptide (residues 10-26) fold into an extended amphipathic alpha-helix at pH 4.0. The orientation of Pol peptide relative to the DPC micelle was investigated using paramagnetic probes at both pH 4.0 and 6.5. These studies show that the peptide inserts deeply into the micelle at pH 4.0, whereas it is more exposed to the aqueous environment at pH 6.5. On the basis of these results, a model which might explain the mechanism of translocation of Pol peptide from acidic endosomes to the cytosol is discussed.

The 11‐mer repeats of human α‐synuclein in vesicle interactions and lipid composition discrimination: A cooperative role

“…[22][23][24][25] Like exchangeable apolipoproteins, the synuclein sequences are characterized by the presence of a set of imperfect 11-residue repeats. On the basis of this 11-mer periodicity, Segrest et al have suggested the possibility that apolipoprotein A-I forms an 11/3 helix with a pitch of 3 turns per 11 residues.…”

Studying the Structure and Dynamics of Biomolecules by Using Soluble Paramagnetic Probes

“…Despite the failure of these compounds to act as neutral sPRE probes, they are nonetheless thought to be useful as a coarse tool to map local electrostatic fields of proteins by NMR spectroscopy 26. Aminoxyl radicals attached to lipophilic anchors have also been developed to monitor amphipathic peptides and membrane proteins in lipid micelle environments 17b,c. 27…”

<div>Phosphorylation of the viral coat protein regulates RNA virus infection</div>

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