The location of coenzyme Q10 in phospholipid membranes made of POPE: a small-angle synchrotron X-ray diffraction study

Abstract

The location of coenzyme Q10 (Q10) inside the inner mitochondrial membrane is a topic of research aiming at a deeper understanding of the function of the mitochondrial respiratory chain. We investigated the location of Q10 inside model membranes made of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine by means of small-angle synchrotron X-ray diffraction. Q10, which stands for ubiquinone-10 (UQ) or ubihydroquinone-10 (UH), did not remarkably influence the main phase transition temperature, but significantly decreased the lamellar-inverse hexagonal phase transition temperature (T(h)). The effect of UH on T(h) was stronger than the effect of UQ and the effect of liquid Q10 on T(h) was stronger than the effect of crystalline Q10. In the presence of Q10, the lattice parameters of the lamellar phases remained unchanged, whereas the H II lattice parameter was clearly influenced: While UQ had an increasing effect, UH had a decreasing effect. Furthermore, Q10 prevented the formation of cubic phases. The results give new evidence that the headgroup of Q10 is distant from the center of the membrane, which might be important for the function of the mitochondrial respiratory chain.

New Insights into the Interaction of Class II Dihydroorotate Dehydrogenases with Ubiquinone in Lipid Bilayers as a Function of Lipid Composition

“…By using multidimensional neutron contrast variation of the lipids and the aqueous solvent, we have directly observed the location of ubiquinone in the bilayers, consistent with previous experiments with neutron diffraction [ 38 ], showing that ubiquinone tends to localize at the center of the lipid bilayer in multilamellar lipid stacks and fills the interstitial space in the inverse hexagonal H II phase of POPE [ 73 ]. Our results clearly indicate a perpendicular orientation of Q 10 relative to the phospholipids.…”

A Soluble Metabolon Synthesizes the Isoprenoid Lipid Ubiquinone

“…Subsequently, seven consecutive chemical reactions modify the head group to yield UQ (Figure 1A). Hydrophobic polyprenylated intermediates of the UQ biosynthetic pathway are predicted to be embedded within the lipid bilayer (Stefely and Pagliarini, 2017), with the head groups near the glycerol backbone of the membrane phospholipids, and the isoprenoid tail inserted between their acyl chains (Galassi and Arantes, 2015;Hoyo et al, 2017;Wollstein et al, 2015). In contrast, the decarboxylase, methyltransferases and hydroxylases of the UQ biosynthetic pathway contain no transmembrane domains and are predicted to be soluble.…”

Mitochondrial Cristae Morphology Reflecting Metabolism, Superoxide Formation, Redox Homeostasis, and Pathology

“…However, for the reduced CoQ, the QH 2 -headgroup is thought to locate and migrate much closer to the lipid bilayer surface. This was suggested by studies of the hydrated hexagonal phase of 1-palmitoyl-2-oleoyl-PE, in which QH 2 headgroups parallelled PE headgroups, whereas Q headgroups were located deeper in the acyl-group region (Wollstein et al, 2015 ). Detailed knowledge on Q/QH 2 migration within cristae membranes (CM) is needed to judge from which pool CoQ binding to Q-binding sites of RC complexes occurs since these sites have distinct positional depth in the bilayer.…”