Power Conversion in Mitochondria I Flashcards
What can flavins accept as part of a reduction process?
2H+ and 2e-
What prosthetic groups do cytochromes contain?
heme
What redox chemistry can hemes do?
Electron reduction going from Fe3+ to Fe2+
What does the midpoint potential of hemes depend on?
the structure of heme and the local environment of proteins
What kind of Fe do Fe-S centres contain?
Non-heme iron
What redox chemistry do Fe-S centres do?
Electron reduction from Fe3+→Fe2+
What role can Copper have in redox proteins?
- Can be single Cu
- Can be in a 2Cu cluster with S atoms
What redox chemistry can ubiquinone do?
- Reduced in 2 sequential steps of electron transfer
- The 2nd step also allows 2H+ to be taken up
What is the maximum distance redox centres can be apart to allow for electron transfer?
15Å
what happens to electron transfer when redox centres are bound to protein?
They are capable of much faster electron transfer
Which amino acids can accept or donate a H+ to become charged?
Glu, Arg, Asp, His, Lys
What do pKa values of amino acids depend on?
Local enviornment and conformational changes to protein
How can H+ move in ETC?
Can move from one amino acid to another along charged residues as electron move down electron wire, the energy is conserved and used to pump H+ against conc gradient
How many core subunits does mitochondrial complex I contain?
46
What are the 2 types of domains in mitochondrial complex I?
- Hydrophobic peripheral domain
- Membrane domain
What is complex I also called?
NADH dehydrogenase
What happens in the hydrophobic domain of complex I?
- NADH oxidised to NAD+ and H+
- 2 electrons passed onto FMN, then passed to 7 Fe-S centres
- Finally 2 electrons passed to Q forming QH2
What does the hydrophobic domain of complex I contain?
Redox cofactors
Does the membrane domain of complex 1 contain redox centres?
No
What happens in membrane domain of complex 1 ?
Pumps H+ across membrane of matrix into intermembrane space
In membrane domain of complex 1 how many H+ are pumped per 2 electrons?
4
What is the structure of membrane domain of complex 1?
- 3 conserved membrane subunits which are homologous to H+/Na+ antiporters
- Proton wire through centre of complex
What likley forms H+ channel in membrane domain of complex 1?
Conserved essential polar and charged residues
What kind of mechanism is used for proton pumping in complex 1?
Indirect mechanism
How does proton pumping occur in complex I?
- electron movement produces energy, dirivng conformational changes
- these cause a shift in pKa of an amino acid and changes in structure to give outward facing conformation
- electrons passed down again resets protein
