TY - JOUR
T1 - Cholesterol is found to reside in the center of a polyunsaturated lipid membrane
AU - Harroun, Thad A.
AU - Katsaras, John
AU - Wassall, Stephen R.
PY - 2008/7/8
Y1 - 2008/7/8
N2 - Previously, we reported neutron diffraction studies on the depth of cholesterol in phosphatidylcholine (PC) bilayers with varying amounts of acyl chain unsaturation [Harroun, T. A., et al. (2006) Biochemistry 45, 1227-1233]. The center of mass of the 2,2,3,4,4,6-D6 deuterated sites on the sterol label was found to reside 16 Å from the middle of the bilayer in 1-palmitoyl-2-oleoylphosphatidylcholine (16:0-18:1PC), 1,2- dioleoylphosphatidylcholine (18:1-18:1PC), and 1-stearoyl-2- arachidonylphosphatidylcholine (18:0-20:4PC). This location places cholesterol's hydroxyl group close to the membrane surface, indicative of the molecule in its commonly understood "upright" orientation. However, for dipolyunsaturated 20:4-20:4PC membranes the label, thus the hydroxyl group, was found sequestered in the center of the bilayer. We attributed the change in location to the high level of disorder of polyunsaturated fatty acids (PUFA) that is incompatible with proximity to the rigid steroid moiety in its usual upright orientation. From that study, the unresolved question was whether the molecule was inverted or lying flat with respect to the membrane plane, in the middle of the bilayer. We have followed up those results with additional neutron experiments employing [25,26,26,26,27,27-D7]cholesterol, a deuterated analogue labeled in the tail. These diffraction measurements unequivocally show cholesterol lies flat in the middle of 20:4-20: 4PC bilayers.
AB - Previously, we reported neutron diffraction studies on the depth of cholesterol in phosphatidylcholine (PC) bilayers with varying amounts of acyl chain unsaturation [Harroun, T. A., et al. (2006) Biochemistry 45, 1227-1233]. The center of mass of the 2,2,3,4,4,6-D6 deuterated sites on the sterol label was found to reside 16 Å from the middle of the bilayer in 1-palmitoyl-2-oleoylphosphatidylcholine (16:0-18:1PC), 1,2- dioleoylphosphatidylcholine (18:1-18:1PC), and 1-stearoyl-2- arachidonylphosphatidylcholine (18:0-20:4PC). This location places cholesterol's hydroxyl group close to the membrane surface, indicative of the molecule in its commonly understood "upright" orientation. However, for dipolyunsaturated 20:4-20:4PC membranes the label, thus the hydroxyl group, was found sequestered in the center of the bilayer. We attributed the change in location to the high level of disorder of polyunsaturated fatty acids (PUFA) that is incompatible with proximity to the rigid steroid moiety in its usual upright orientation. From that study, the unresolved question was whether the molecule was inverted or lying flat with respect to the membrane plane, in the middle of the bilayer. We have followed up those results with additional neutron experiments employing [25,26,26,26,27,27-D7]cholesterol, a deuterated analogue labeled in the tail. These diffraction measurements unequivocally show cholesterol lies flat in the middle of 20:4-20: 4PC bilayers.
UR - http://www.scopus.com/inward/record.url?scp=46849085354&partnerID=8YFLogxK
U2 - 10.1021/bi800123b
DO - 10.1021/bi800123b
M3 - Article
C2 - 18543943
AN - SCOPUS:46849085354
SN - 0006-2960
VL - 47
SP - 7090
EP - 7096
JO - Biochemistry
JF - Biochemistry
IS - 27
ER -