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Open AccessArticle

Comparing Interfacial Trp, Interfacial His and pH Dependence for the Anchoring of Tilted Transmembrane Helical Peptides

1
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
2
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
*
Author to whom correspondence should be addressed.
Biomolecules 2020, 10(2), 273; https://doi.org/10.3390/biom10020273
Received: 16 January 2020 / Revised: 7 February 2020 / Accepted: 10 February 2020 / Published: 11 February 2020
(This article belongs to the Special Issue Advances in Membrane Proteins)
Charged and aromatic amino acid residues, being enriched toward the terminals of membrane-spanning helices in membrane proteins, help to stabilize particular transmembrane orientations. Among them, histidine is aromatic and can be positively charged at low pH. To enable investigations of the underlying protein–lipid interactions, we have examined the effects of single or pairs of interfacial histidine residues using the constructive low-dynamic GWALP23 (acetyl-GG2ALW5LALALALALALALW19LAG22A-amide) peptide framework by incorporating individual or paired histidines at locations 2, 5, 19, or 22. Analysis of helix orientation by means of solid-state 2H NMR spectra of labeled alanine residues reveals marked differences with H2,22 compared to W2,22. Nevertheless, the properties of membrane-spanning H2,22WALP23 helices show little pH dependence and are similar to those having Gly, Arg, or Lys at positions 2 and 22. The presence of H5 or H19 influences the helix rotational preference but not the tilt magnitude. H5 affects the helical integrity, as residue 7 unwinds from the core helix; yet, once again, the helix orientation and dynamic properties show little sensitivity to pH. The overall results reveal that the detailed properties of transmembrane helices depend upon the precise locations of interfacial histidine residues.
Keywords: transmembrane helix; interfacial aromatic ring; solid-state deuterium NMR; tryptophan; histidine transmembrane helix; interfacial aromatic ring; solid-state deuterium NMR; tryptophan; histidine
MDPI and ACS Style

Afrose, F.; Koeppe II, R.E. Comparing Interfacial Trp, Interfacial His and pH Dependence for the Anchoring of Tilted Transmembrane Helical Peptides. Biomolecules 2020, 10, 273.

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