Illuminating Disorder Induced by Glu in a Stable Arg-Anchored Transmembrane Helix

Abstract

Membrane proteins are vital for biological function and are complex to study. Even in model peptide-lipid systems, the combined influence or interaction of pairs of chemical groups still is not well understood. Disordered proteins, whether in solution or near lipid membranes, are an emerging paradigm for the initiation and control of biological function. The disorder can involve molecular orientation as well as molecular folding. This paper reports an astonishing induction of disorder when one Glu residue is introduced into a highly stable 23-residue transmembrane helix. The parent helix is anchored by a single Arg residue, tilted at a well-defined angle with respect to the DOPC bilayer normal and undergoes rapid cone precession. When Glu is introduced two residues away from Arg, with 200° (or 160°) radial separation, the helix properties change radically to exhibit a multiplicity of three or more disordered states. The helix characteristics have been monitored by deuterium (2H) NMR spectroscopy as functions of the pH and lipid bilayer composition. The disordered multistate behavior of the (Glu, Arg)-containing helix varies with the lipid bilayer thickness and pH. The results highlight a fundamental induction of protein multistate properties by a single Glu residue in a lipid membrane environment.

D-to-E and T19V Variants of the pH-Low Insertion Peptide and Their Doxorubicin Conjugates Interact with Membrane at Higher pH Ranges Than WT

“…The insertion of pHLIP is unidirectionalonly the C-terminus is translocated across the membrane. ,,, In the final TM state, the D14 and D25 residues are located in the hydrophobic core of the membrane, while the C-terminal D31, D33, and E34 residues are positioned in the headgroup region of the trans lipid leaflet . These features make pHLIP an intriguing model for understanding how the protonation states of Asp/Glu residues can influence the folding and topogenesis of a TM α-helixan important topic that has been explored in the context of other TM or membrane-bound helices such as pLeu­(D), , GALA, − GWALP23­(E), − MelP5­(Δ4/6), pHD, − macrolittins, PLP TM2, CFTR TM4, diphtheria toxin T-domain TH8-TH9, − and others. , Interestingly, the pH-dependent membrane insertion behavior of pHLIP can even be obtained by grafting the key Asp/Glu residues onto completely different background TM sequences, such as in the ATRAM peptide, and the TYPE7 peptide that can activate the receptor EphA2 …”