TAILIEUCHUNG - Báo cáo khoa học: Structure and topology of the transmembrane domain 4 of the divalent metal transporter in membrane-mimetic environments

The divalent metal transporter (DMT1) is a 12-transmem-brane domain protein responsible for dietary iron uptake in the duodenum and iron acquisition from transferrin in peripheral tissues. The transmembrane domain 4 (TM4) of DMT1 has been shown to be crucial for its biological function. Here we report the 3D structure and topology of the DMT1-TM4 peptide by NMR spectroscopy with simulated annealing calculations in membrane-mimetic environments, . 2,2,2-trifluoroethanol and SDS micelles. The 3D structures of the peptide are similar in both envi-ronments, with nonordered and flexible N- and C-termini flanking an ordered helical region. . | Eur. J. Biochem. 271 1938-1951 2004 FEBS 2004 doi Structure and topology of the transmembrane domain 4 of the divalent metal transporter in membrane-mimetic environments Hongyan Li1 2 Fei Li1 Zhong Ming Qian2 and Hongzhe Sun1 1 Department of Chemistry and Open Laboratory of Chemical Biology The University of Hong Kong China department of Applied Biology and Chemical Technology The Hong Kong Polytechnic University Hong Kong China The divalent metal transporter DMT1 is a 12-transmem-brane domain protein responsible for dietary iron uptake in the duodenum and iron acquisition from transferrin in peripheral tissues. The transmembrane domain 4 TM4 of DMT1 has been shown to be crucial for its biological function. Here we report the 3D structure and topology of the DMT1-TM4 peptide by NMR spectroscopy with simulated annealing calculations in membrane-mimetic environments . 2 2 2-trifluoroethanol and SDS micelles. The 3D structures of the peptide are similar in both environments with nonordered and flexible N- and C-termini flanking an ordered helical region. The final set of the 16 lowest energy structures is particularly well defined in the region of residues Leu9-Phe20 in 2 2 2-trifluoroethanol with a mean pairwise root mean square deviation of A for the backbone heavy atoms and A for all heavy atoms. In SDS micelles the length of the helix is dependent on pH values. In particular the C-terminus becomes well-structured at low pH whereas the N-terminal segment Arg1-Gly7 is flexible and poorly defined at all pH values studied. The effects of 12-doxylPtdCho spin-label and paramagnetic metal ions on NMR signal intensities demonstrated that both the N-ter-minus and helical region of the TM4 are embedded into the interior of SDS micelles. Unexpectedly we observed that amide protons exchanged much faster in SDS than in 2 2 2-trifluoroethanol indicating that there is possible solvent accessibility in the structure. The

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