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Proton translocation by transhydrogenase.

J Baz Jackson¹

¹School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. j.b.jackson@bham.ac.uk

|June 6, 2003

Summary

Transhydrogenase enzymes couple hydride transfer to proton movement using alternating open and occluded conformations. This conformational change mechanism facilitates redox reactions essential for cellular energy.

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Area of Science:

Biochemistry
Molecular Biology
Cellular Respiration

Background:

Transhydrogenase enzymes are crucial for cellular energy metabolism, linking hydride transfer between NADH and NADP+ to proton translocation across membranes.
These enzymes are found in animal mitochondria and bacteria, playing a vital role in maintaining cellular redox balance.

Purpose of the Study:

To elucidate the mechanism by which transhydrogenase couples hydride transfer to proton translocation.
To understand the role of conformational changes in regulating the enzyme's activity during turnover.

Main Methods:

The study likely involved structural biology techniques (e.g., X-ray crystallography, cryo-EM) to visualize enzyme conformations.
Biochemical assays were probably used to monitor hydride transfer and proton translocation rates.

Main Results:

Transhydrogenase utilizes distinct 'open' and 'occluded' conformations to regulate substrate binding, product release, and hydride transfer.
The dihydronicotinamide and nicotinamide rings are positioned apart in the open state and brought together in the occluded state, enabling redox chemistry.
Conformational changes occur in a reciprocating, out-of-phase manner between the enzyme's two monomers during catalytic turnover.

Conclusions:

The conformational alternation mechanism is key to the function of transhydrogenase, ensuring efficient coupling of redox reactions and proton transport.
Understanding this mechanism provides insights into cellular energy production and potential targets for therapeutic intervention.

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