Structure and transmembrane topology of Slc11a1 TMD1-5 in lipid membranes.

Jiantao Li, Lingling Wang, Li Wang, Fei Li

State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, People's Republic of China.

Biopolymers 2012

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The importance of solute carrier family 11 (Slc11) in divalent metal-ion transport has been well established. The core domains TMD1-5 and TMD6-10 of the proteins were modeled as a symmetric but inversely orientated arrangement with respect to membrane normal. In this article, the structures and transmembrane topologies of TMD1-5 of Slc11a1 incorporated with phospholipids 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (POPG), and POPC/POPG (3:1) were explored using circular dichroism, fluorescence, and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies. The segments TMD2-5 were inserted in lipid membranes mainly as an α-helix with orientations of helices along membrane normal. The tilt angles of the helices were in an order of TMD3 > TMD4 > TMD2 > TMD5 in these membranes. In contrast, TMD1 was partly inserted in membranes, leaving partial segment at membrane surface. The amount of the lipid component with negatively charged headgroups had an effect on both the helicity and orientation of the transmembrane domains (TMDs). Nevertheless, the helices maintained similar topologies in various membranes. Copyright © 2012 Wiley Periodicals, Inc.

Citation

Jiantao Li, Lingling Wang, Li Wang, Fei Li. Structure and transmembrane topology of Slc11a1 TMD1-5 in lipid membranes. Biopolymers. 2012;98(3):224-33