Premium
The third and fourth transmembrane domains of Slc11a1: Comparison of their structures and positioning in phospholipid model membranes
Author(s) -
Qi Haiyan,
Yang Lei,
Xue Rong,
Song Yuande,
Wang Shuo,
Li Fei
Publication year - 2008
Publication title -
peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.21115
Subject(s) - chemistry , phospholipid , membrane , transmembrane protein , biophysics , biochemistry , receptor , biology
Interactions of two peptides TM3 and TM4, corresponding to the third and fourth transmembrane domains of a divalent metal‐ion transporter Slc11a1, respectively, with phospholipid model membranes, including zwitterionic dimyristoylphosphatidylcholine (DMPC) and anionic dimyristoylphosphatidylglycerol (DMPG), are studied in a wide range of peptide‐to‐lipid ( P : L ) ratios, and the secondary structures and positioning of the peptides in the lipid bilayers are analyzed, using differential scanning calorimetry (DSC), circular dichroism (CD), and fluorescence techniques. DSC and fluorescence results indicate that both peptides are inserted in the phospholipid bilayers. TM4 is buried in the bilayers more deeply and the insertion position is less affected by pH values, whereas TM3 is less deeply embedded and the position is remarkably shifted toward the direction of the bilayer surface with increasing pH value. The incorporation of TM4 in both lipids causes more perturbation to the packing of the hydrophobic chains of the lipids than TM3. Moreover, the perturbation of TM3 to the lipid packing is pH dependent, whereas the perturbation of TM4 is less pH dependent but with an unusually larger change in the enthalpy of the main transition at pH 5.5 than those at pH 4 and 7. CD data demonstrate that the main discrimination between the secondary structures of TM4 and TM3 is the α‐helix content, more helicity for TM4 than TM3 in both lipids. The folding of the peptides is also affected by the composition of the phospholipids. Anionic lipid DMPG induces more α‐helical folding than neutral lipid DMPC for both peptides. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 92: 52–64, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com