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The mitochondrial proton-pumping respiratory
complex I
The proton-pumping NADH:ubiquinone oxidoreductase, also called complex
I, is the first of the respiratory complexes providing the proton
motive force which is essential for the synthesis of ATP. We try to
understand the assembly, structure and function of this enzyme using
the fungus Neurospora crassa as model organism. Our current
research basically follows two lines.
A major goal of our studies is to understand the processes linking
electron and proton translocation. While the epr detectable iron-sulfur
clusters and the FMN which are prosthetic groups of the matrix arm of
complex I are rather well characterized, very little is known about
redox reactions taking place in the membrane arm. Employing time
resolved UV/VIS-spectroscopy we try to gain access to so far
uncharacterized redox groups. The biggest challenge posed by complex I
is the elucidation of its high resolution structure. All efforts to
clarify the enzymatic mechanism of complex I are futile without
knowledge of the detailed three-dimensional structure. To this end we
crystallize complex I and its subcomplexes for x-ray analysis.
The second focus is the identification of proteins involved in the
assembly of
the complex. Two subunits of complex I, one functioning as acyl carrier
protein and the other being a NADPH-dependent reductase/isomerase,
appear to have biosynthetic functions. Two other proteins, designated
CIA proteins, have been characterized which are associated transiently
with an assembly intermediate of complex I and might be complex I
specific chaperone type proteins.
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