Solution structure of neuromedin B by 1H nuclear magnetic resonance spectroscopy

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The solution structure of neuromedin B (NMB) was investigated using two-dimensional nuclear magnetic resonance (NMR) spectroscopy in membrane-mimicking environments. NMB adopts a relaxed helical conformation from Trp 4 to Met 10 in 50% aqueous 2,2,2-trifluoroethanol (TFE) solution and in 150 mM SDS micelles. Sidechain atoms of the three residues, Trp 4, His 8 and Phe 9 orient toward the same direction and these residues might play a key role on interacting with hydrophobic acyl chains of the phospholipids in the membrane. NOESY experiments performed on NMB in non-deuterated SDS micelle show that aromatic ring protons of Trp 4 and Phe 9 residues are in close contact with methylene protons of SDS micelles. In addition, proton longitudinal relaxation data proved that the interactions between NMB with SDS micelle are characterized as extrinsic interaction. Trp 4 and Phe 9 seem to be important in interaction with receptor and this agrees with the previous studies of structure-activity relationship (Howell, D.C. et al. (1996) Int. J. Pept. Protein Res. 48, 522–531). These conformational features might be helpful in understanding the molecular mechanism of the function of NMB and developing the efficient drugs.