The d subunit plays a central role in human vacuolar H(+)-ATPases

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biophysics

Background:

• Vacuolar-type H(+)-ATPase (V-ATPase) is a multi-subunit proton pump essential for cellular functions.
• The V(0) domain facilitates proton translocation, but the precise role and localization of the mammalian d subunit remain poorly understood.
• Two isoforms, d1 and d2, exist with distinct expression patterns, suggesting specialized functions.

Purpose of the Study:

• To elucidate the function and localization of the human V-ATPase d1 and d2 subunits within the proton pump.
• To determine if the d subunit interacts with the central stalk components (D and F subunits) of the V-ATPase.

Main Methods:

• In silico structural modeling of human d1 and d2 subunits.
• Expression studies using human kidney membrane preparations to assess subunit interactions.
• In vitro binding assays with purified D and F subunits.

Main Results:

• Human d1 and d2 subunits are structural orthologues of bacterial V-ATPase subunit C.
• Both d1 and d2 isoforms directly interact with the central stalk subunits D and F.
• These interactions were confirmed using both membrane preparations and purified proteins.

Conclusions:

• The mammalian V-ATPase d subunit is centrally located within the proton pump, likely forming part of the central stalk.
• The d subunit plays a critical role in the rotary mechanism of the V-ATPase, facilitating proton translocation.
• This study clarifies the structural organization and functional significance of the V-ATPase d subunit.