Human
dihydroorotate dehydrogenase (
DHODH) catalyzes the fourth step of the de novo
pyrimidine biosynthesis pathway and uses
ubiquinone Q10, a lipophilic molecule located in the inner mitochondrial membrane (IMM), as its co-substrate.
DHODH is anchored to the IMM by a single transmembrane helix located at its N-terminus. Nevertheless, how
DHODH function is determined by its surrounding membrane environment and
protein-
lipid interactions, as well as the mechanism by which
ubiquinone Q10 accesses the active site of
DHODH from within the membrane are still largely unknown. Here, we describe the interaction between wild-type
DHODH and three
DHODH mutants associated with
Miller syndrome and
lipids using enzymatic assays, thermal stability assays and
Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). Our results provide evidence indicating that the N-terminal part of human
DHODH is not only a structural
element for mitochondrial import and location of
DHODH, but also influences enzymatic activity and utilization of
ubiquinone Q10 and
ubiquinone analogues in in vitro assays. They also support the role of tetraoleoyl
cardiolipin as a
lipid interacting with
DHODH. Additionally, the results from QCM-D show that the
Miller syndrome mutants studied differ in their interactions with supported
lipid bilayers compared to wild-type
DHODH. These altered interactions add another dimension to the effects of mutations found in
Miller syndrome. To the best of our knowledge, this is the first investigation of the
protein-
lipid interactions of
DHODH variants associated with
Miller syndrome.