The role of a conserved tyrosine in the 49-kDa subunit of complex I for ubiquinone binding and reduction

作者：Tocilescu Maja A; Fendel Uta; Zwicker Klaus; Droese Stefan; Kerscher Stefan; Brandt Ulrich^*

来源：Biochimica et Biophysica Acta-Bioenergetics, 2010, 1797(6-7): 625-632.

DOI：10.1016/j.bbabio.2010.01.029

• Mitochondria
• Complex I
• Ubiquinone
• Inhibitor resistance
• Mutagenesis
• Yarrowia lipolytica

Iron-sulfur cluster N2 of complex I (proton pumping NADH:quinone oxidoreductase) is the immediate electron donor to ubiquinone. At a distance of only similar to 7 angstrom in the 49-kDa subunit, a highly conserved tyrosine is found at the bottom of the previously characterized quinone binding pocket. To get insight into the function of this residue, we have exchanged it for six different amino acids in complex I from Yarrowia Mitochondrial membranes from all six mutants contained fully assembled complex I that exhibited very low dNADH:ubiquinone oxidoreductase activities with n-decylubiquinone. With the most conservative exchange Y144F, no alteration in the electron paramagnetic resonance spectra of complex I was detectable. Remarkably, high dNADH:ubiquinone oxidoreductase activities were observed with ubiquinones Q(1) and Q(2) that were coupled to proton pumping. Apparent K(m) values for Q(1) and Q(2) were markedly increased and we found pronounced resistance to the complex I inhibitors decyl-quinazoline-amine (DQA) and rotenone. We conclude that Y144 directly binds the head group of ubiquinone, most likely via a hydrogen bond between the aromatic hydroxyl and the ubiquinone carbonyl. This places the substrate in an ideal distance to its electron donor iron-sulfur cluster N(2) for efficient electron transfer during the catalytic cycle of complex I.

• 出版日期2010-7