[Spatial structure of bacterioopsin transmembrane segments C, E, and G from two-dimensional 1H-NMR data]

The spatial structure of synthetic peptides with transmembrane segment sequences C (residues 67-106), E (128-162), and G (190-233) of bacterioopsin from Halobacterium halobium solubilized in methanol-chloroform 1:1 containing 0.1 M LiClO4 was computed based on 2D 1H NMR data. Segment C forms a right alpha-helix between Pro77 and Val101. The residue Pro91 within the alpha-helix induces a 25 degrees "kink". Segment E forms a right alpha-helix between Val136 and Ser158. Segment G includes alpha-helical region, which begins from CO of Ile198 and ends at N alpha-H of Arg227. The torsion angles, chi 1, of the side chains were unambiguously determined for most of the residues within the alpha-helical regions. Conformations of some side chains of the transmembrane segment residues in the solution were found to differ from their previously reported conformations determined by electron microscopy. Conformations of the sites terminating the C and E segment alpha-helices were refined.