Structure analysis of the fourth transmembrane domain of Nramp1 in model membranes.
Nramp1 (natural resistance-associated macrophage protein 1) is an integral membrane protein with 12 putative transmembrane domains. As a proton-coupled divalent metal cation transporter, it is involved in defense against intracellular pathogens. Disease-causing mutation in Nramp1 occurring at glycine 169 located within the fourth transmembrane domain (TM4) suggests functional importance of this domain. In this paper, we study the three-dimensional structures of a peptide, corresponding to the TM4 of the wild-type Nramp1, in SDS micelles and 2, 2, 2-trifluoroethanol solvent using CD and NMR spectroscopies. We have found that an alpha-helix is predominantly induced in membrane-mimetic environments and the folding of the C-terminal residues is regulated by pH in SDS micelles. The peptide is embedded in SDS micelles and self-associated by coiled-coil interactions. The helix of the peptide in TFE is lengthened towards the N-terminus compared with those in SDS micelles at acidic pH and the self-association of the peptide is also observed in TFE. The fact that Mn(2+) ions are accessible to Asp-14 located in the interior of SDS micelles is found and the binding affinity is increased with increasing pH. The self-association of the peptide may provide a path by which Mn(2+) ions pass through the membrane.
Xue
Rong
R
State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, PR China.
Wang
Shuo
S
Qi
Haiyan
H
Song
Yuande
Y
Wang
Chunyu
C
Li
Fei
F
D000818:Animals; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002413:Cations, Divalent / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D017136:Ion Transport / Q000235:genetics; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008823:Micelles; D009154:Mutation; D010455:Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000235:genetics; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D000099173:Natural Resistance-associated Macrophage Protein 1
D027682:Cation Transport Proteins; D002413:Cations, Divalent; D008345:Manganese; D008823:Micelles; D010455:Peptides; D012967:Sodium Dodecyl Sulfate; D000099173:Natural Resistance-associated Macrophage Protein 1