Proton-translocating transhydrogenase: an update of unsolved and controversial issues

Area of Science:

• Biochemistry and Molecular Biology
• Membrane Protein Function
• Energy Transduction

Background:

• Proton-translocating transhydrogenases are essential membrane enzymes that generate NADPH, vital for maintaining cellular redox balance, particularly reduced glutathione.
• While the structure and hydride transfer mechanism of soluble domains are known, the intact enzyme structure and proton translocation mechanism remain elusive.

Purpose of the Study:

• To investigate the roles of soluble substrate-binding domains in the proton translocation mechanism of transhydrogenases.
• To elucidate how these domains communicate with the membrane-bound portion of the enzyme.
• To understand the mechanism of proton translocation across the membrane.

Main Methods:

• Utilized separately expressed soluble substrate-binding domains (NADP(H)-binding and NAD(H)-binding domains) of proton-translocating transhydrogenases.
• Investigated the functions and properties of these domains relevant to proton translocation and inter-domain communication.

Main Results:

• Identified key functions and properties of the soluble NADP(H) and NAD(H)-binding domains that are critical for proton translocation.
• Provided insights into the communication pathways between the soluble domains and the membrane-bound domain.
• Advanced the understanding of the proton translocation mechanism across the membrane.

Conclusions:

• The soluble domains of proton-translocating transhydrogenases play a significant role in the enzyme's overall mechanism, including proton translocation.
• Understanding these domains is crucial for deciphering the complete mechanism of NADPH generation and cellular redox maintenance.
• Further research on the intact enzyme structure is needed to fully resolve the proton translocation process.