Ionization Properties of Histidine Residues in the Lipid Bilayer Membrane Environment

Martfeld, Ashley N.; Greathouse, Denise V.; Koeppe, Roger E.

doi:10.1074/jbc.m116.738583

Cited by 28 publications

(42 citation statements)

References 51 publications

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“…When the pH is raised from 6 to 13 in DLPC-ether bilayers, there are no observed changes in ∣Δψ q ∣ values for the CD 3 groups of the core alanines (Table 1, Figure 7A). This is a distinct contrast to the results for the E14 and E16 peptides, yet indicates striking agreement with results for GWALP23-H12 in DLPC [28]. Indeed, when the central residue 12 is modified, the 2 H NMR spectra for both GWALP23-E12 and GWALP23-H12 in DLPC bilayers appear to be independent of pH.…”

Section: Resultssupporting

confidence: 80%

“…The (presumably) neutral E14 peptide adopts a tilted conformation in DLPC distinct from that of the host peptide, attributable to the presence of a polar residue at position 14 and similar to the observations with GWALP23-H14 in DLPC bilayers [28]. The incorporation of a (neutral) polar residue at position 14, be it His or Glu, interestingly results in a −40° to −50° change in rotation about the helix axis (Table 2 and [21, 28]). The results confirm that a polar residue at position 14 modulates the orientation of the helix in DLPC.…”

Section: Discussionsupporting

confidence: 75%

“…It is of further interest that the terminal unwinding of the –E12 peptide in DLPC, while present, shows no inclination to change with pH, unlike the changes observed with E14 and E16 that seem to alter the interfacial layer access for the Glu residue at high pH. Rather, GWALP23-E12 seems to exist in the DLPC bilayer in the same single orientation throughout the pH range, similar to observations with GWALP23-H12 [28]. …”

Section: Resultssupporting

confidence: 64%

“…Indeed, the 2 H quadrupolar splitting magnitudes ∣Δν q ∣ of not only the outer alanines 3 and 21 but also A17 (considered within the “core” domain) deviate and fail to fit the helix backbone geometry (Figure 4). This situation is unique for glutamic acid, as deviations from the core helix geometry have not been observed for R14 [8] or K14 [21] or H14 [28]. The observed deviations from the quadrupolar wave that corresponds to the backbone of the core helix (Figure 4) are 2 kHz for A3, 5 kHz for A17 and 10 kHz for A21 (in the context of an experimental uncertainty of 1 kHz).…”

Section: Resultsmentioning

confidence: 89%

“…The collective ∣Δψ q ∣ magnitudes (Table 1) reveal a well-defined transmembrane orientation, with minor fraying near residues 3 and 21, for GWALP23-E12 in DLPC (Figure 8). Comparing the results for E12 with GWALP23-H12 [28] reveals only small differences in helix tilt Δτ and azimuthal rotation Δρ (about 0.3° and 3°, respectively), when H12 is replaced with E12. The substituted helices, with a polar residue at position 12, furthermore have the same helix tilt and rotation as the parent L12 helix of GWALP23 (Table 2).…”

Section: Resultsmentioning

confidence: 99%

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Influence of glutamic acid residues and pH on the properties of transmembrane helices

Rajagopalan¹,

Greathouse²,

Koeppe³

2017

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Negatively charged side chains are important for the function of particular ion channels and certain other membrane proteins. To investigate the influence of single glutamic acid side chains on helices that span lipid-bilayer membranes, we have employed GWALP23 (acetyl-GGALW5LALALALALALALW19LAGA-amide) as a favorable host peptide framework. We substituted individual Leu residues with Glu residues (L12E or L14E or L16E) and incorporated specific 2H-labeled alanine residues within the core helical region or near the ends of the sequence. Solid-state 2H-NMR spectra reveal little change for the core labels in GWALP23-E12, –E14 and –E16 over a pH range of 4 to 12.5, with the spectra being broader for samples in DOPC compared to DLPC bilayers. The spectra for samples with deuterium labels near the helix ends on alanines 3 and 21 show modest pH-dependent changes in the extent of unwinding of the helix terminals in DLPC and DOPC bilayers. The combined results indicate minor overall responses of these transmembrane helices to changes in pH, with the most buried residue E12 showing no pH dependence. While the Glu residues E14 and E16 may have high pKa values in the lipid bilayer environment, it is also possible that a paucity of helix response is masking the pKa values. Interestingly, when E16 is present, spectral changes at high pH report significant local unwinding of the core helix. Our results are consistent with the expectation that buried carboxyl groups aggressively hold their protons and/or waters of hydration.

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Section: Resultssupporting

confidence: 80%

Section: Discussionsupporting

confidence: 75%

Section: Resultssupporting

confidence: 64%

Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

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Influence of glutamic acid residues and pH on the properties of transmembrane helices

Rajagopalan¹,

Greathouse²,

Koeppe³

2017

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Flanking aromatic residue competition influences transmembrane peptide helix dynamics

2020

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To address biophysical principles and lipid interactions that underlie the properties of membrane proteins, modifications that vary the neighbors of tryptophan residues in the highly dynamic transmembrane helix of GW 4,20 ALP23 (acetyl-GGAW 4 A(LA) 6 LAW 20 AGA-amide) were examined using deuterium NMR spectroscopy. It was found that L 5,19 GW 4,20 ALP23, a sequence isomer of the low to moderately dynamic GW 5,19 ALP23, remains highly dynamic. By contrast, a removal of W4 to produce F 4,5 GW 20 ALP23 restores a low level of dynamic averaging, similar to that of the F 4,5 GW 19 ALP23 helix. Interestingly, a high level of dynamic averaging requires the presence of both tryptophan residues W4 and W20, on opposite faces of the helix, and does not depend on whether residue 5 is Leu or Ala. Aspects of helix unwinding and potential oligomerization are discussed with respect to helix dynamic averaging and the locations of particular residues at a phosphocholine membrane interface.

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Influence of Lipid Saturation, Hydrophobic Length and Cholesterol on Double‐Arginine‐Containing Helical Peptides in Bilayer Membranes

et al. 2019

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Membrane proteins are essential for many cell processes yet are more difficult to investigate than soluble proteins. Charged residues often contribute significantly to membrane protein function. Model peptides such as GWALP23 (acetyl‐GGALW5LAL8LALALAL16ALW19LAGA‐amide) can be used to characterize the influence of specific residues on transmembrane protein domains. We have substituted R8 and R16 in GWALP23 in place of L8 and L16, equidistant from the peptide center, and incorporated specific 2H‐labeled alanine residues within the central sequence for detection by solid‐state 2H NMR spectroscopy. The resulting pattern of [2H]Ala quadrupolar splitting (Δνq) magnitudes indicates the core helix for R8,16GWALP23 is significantly tilted to give a similar transmembrane orientation in thinner bilayers with either saturated C12:0 or C14:0 acyl chains (1,2‐dilauroyl‐sn‐glycero‐3‐phosphocholine (DLPC) or 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (DMPC)) or unsaturated C16:1 Δ9 cis acyl chains. In bilayers of 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC; C18:1 Δ9 cis) multiple orientations are indicated, whereas in longer, unsaturated 1,2‐dieicosenoyl‐sn‐glycero‐3‐phosphocholine (DEiPC; C20:1 Δ11 cis) bilayers, the R8,16GWALP23 helix adopts primarily a surface orientation. The inclusion of 10–20 mol % cholesterol in DOPC bilayers drives more of the R8,16GWALP23 helix population to the membrane surface, thereby allowing both charged arginines access to the interfacial lipid head groups. The results suggest that hydrophobic thickness and cholesterol content are more important than lipid saturation for the arginine peptide dynamics and helix orientation in lipid membranes.

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Ionization Properties of Histidine Residues in the Lipid Bilayer Membrane Environment

Cited by 28 publications

References 51 publications

Influence of glutamic acid residues and pH on the properties of transmembrane helices

Influence of glutamic acid residues and pH on the properties of transmembrane helices

Flanking aromatic residue competition influences transmembrane peptide helix dynamics

Influence of Lipid Saturation, Hydrophobic Length and Cholesterol on Double‐Arginine‐Containing Helical Peptides in Bilayer Membranes

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