Orientation and conformation of lipids in crystals of transmembrane proteins.

摘要: Orientational order parameters and individual dihedral torsion angles are evaluated for phospholipid glycolipid molecules that resolved in X-ray structures of integral transmembrane proteins crystals. The the lipid chains glycerol backbones protein crystals characterised by a much wider distribution orientational than is found fluid bilayers reconstituted lipid-protein membranes. This indicates lipids membrane mostly not representative entire interface. Much chain configurational disorder membrane-bound arises from C-C bonds energetically disallowed skew conformations. suggests heterogeneity at single binding site: eclipsed conformations occur also backbone head groups. Conformations restricted to gauche C1-C2 rotamers invariably bilayer Lipid head-group do conform solely bent-down conformation, with gauche-gauche configuration phosphodiester, characteristic Stereochemical violations protein-bound evidenced ester carboxyl groups non-planar configurations, even cis configuration. Some have incorrect enantiomeric backbone, many branched methyl phytanyl associated bacteriorhodopsin S