Three-dimensional NMR structure of the sixth ligand-binding module of the human LDL receptor: comparison of two adjacent modules with different ligand binding specificities

The sixth ligand-binding module of the low-density lipoprotein receptor con tributes to the binding of apolipoprotein B100-containing lipoproteins. H-1 NMR spectroscopy, DYANA and X-PLOR structure calculations were used to det ermine that this module has a well defined structure with a backbone confor mation similar to other modules. Structures from calculations that simulate d the presence of a calcium ion showed increased resolution without large i ncreases in energy, increased deviations from idealised geometry or violati ons of experimental constraints. Investigation of the surface properties of this module indicates there are significant differences from the fifth mod ule, which binds apolipoprotein E-containing lipoproteins in addition to ap olipoprotein B100-containing lipoproteins. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserv ed.