Crystallization of human low density lipoprotein (LDL), a large lipid-protein complex - Collection of X-ray data at very low resolution

Human LDL subfractions LDL-2 (d = 1.031-1.034 g/ml) and LDL-5 (d = 1.040-1. 044 g/ml) were crystallized in different crystal forms using polyethylene g lycol as a precipitant. Both fractions were from one donor. Crystals of LDL -5 were yellow, hexagonal, and showed no dichroism. Of LDL-2 two dichroitic crystal forms were obtained. One had a rod-like shape with deep notches at both ends (form A), the other was a more compact form with plain surfaces (form B). To be able to measure low order reflections down to 300 Angstrom a special experimental setup was developed. One single crystal was used to obtain a complete native data set of LDL-2 (form A) with an overall interna l R-factor of 4.5% for reflections from 100 to 28 Angstrom. Data were colle cted under cryogenic conditions using synchrotron radiation. The space grou p is most probably C2 with unit cell dimensions of a = 183 Angstrom b = 421 Angstrom, c = 385 Angstrom, alpha = gamma = 90 degrees, beta approximate t o 90 degrees. Further optimization of the crystallization conditions and th e search for heavy metal derivatives are in progress. (C) 1999 Elsevier Sci ence B.V. All rights reserved.