Marsh Derek
Max-Planck-Institut für biophysikalische Chemie, 37070 Göttingen, Germany.
Protein Sci. 2003 Sep;12(9):2109-17. doi: 10.1110/ps.0396803.
Dihedral angles are evaluated for the phospholipid ligands of the lipid-binding proteins found in the Protein Data Base (PDB). Phospholipid structures occur with a trans C1-C2 configuration of the glycerol backbone and oppositely extended chains, in addition to the gauche C1-C2 rotamers found in membranes. Headgroup conformations are not restricted to the single bent-down configuration and gauche-gauche configuration of the phosphodiester that is found in phospholipid crystals. Additionally, fully extended headgroups and orientations directed away from the lipid chains are found for phospholipids in the protein binding pockets. On average, the hydrocarbon chains of the protein-bound lipids are conformationally more disordered than in fluid bilayer membranes. However, much of this configurational disorder arises from energetically disallowed skew conformations. This suggests a configurational heterogeneity in the lipids at a single binding site: Eclipsed conformations occur also in some lipid headgroups and glycerol backbones. Stereochemical violations appear for some of the ester carboxyl groups of the protein-bound phospholipids in the PDB, and two glycerol backbones have the incorrect enantiomeric configuration.
对蛋白质数据库（PDB）中发现的脂质结合蛋白的磷脂配体进行二面角评估。除了在膜中发现的C1-C2 gauche旋转异构体之外，磷脂结构还以甘油主链的反式C1-C2构型和相反延伸的链出现。头部基团构象并不局限于磷脂晶体中发现的磷酸二酯的单一下弯构型和gauche-gauche构型。此外，在蛋白质结合口袋中的磷脂还发现了完全伸展的头部基团和远离脂质链的取向。平均而言，与蛋白质结合的脂质的烃链在构象上比在流体双层膜中更无序。然而，这种构型无序大多源于能量上不允许的扭曲构象。这表明在单个结合位点的脂质中存在构型异质性：在一些脂质头部基团和甘油主链中也会出现重叠构象。PDB中与蛋白质结合的磷脂的一些酯羧基出现了立体化学违规情况，并且两个甘油主链具有不正确的对映体构型。
