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#V-ATPase

2 public questions tagged with this topic.

Membrane Transportation

Which ATPase is involved in pH regulation in lysosomes and vacuoles?

V-class ATPases also called V-type vacuolar H+-ATPases are large multi-subunit rotary pumps related to F-type ATP synthases but functioning as ATP-driven proton pumps rather than ATP synthetic machines. Complex comprises peripheral V1 sector containing eight subunits including A3B3 hexamer that hydrolyzes ATP and membrane integral Vo sector with proteolipid c-ring, subunit a and accessory subunits mediating proton translocation. Hydrolysis-driven rotation of central stalk couples to c-ring rotation within Vo pumping H+ into lumen. In cells V-ATPase localizes to lysosomes, endosomes, vacuoles,

Ref: Forgac, Nat Rev Mol Cell Biol 2007, Vacuolar H+-ATPases; Alberts, 7th ed., Chapter 13 acidification.

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Membrane Transportation

Which pump is responsible for maintaining low pH in lysosomes?

Lysosomes function as degradative centers requiring low internal pH between 4.5 and 5 to activate more than fifty acid hydrolases such as cathepsins, sulfatases and lipases, while protecting cytosol from unwanted proteolysis. Acidic environment established primarily by vacuolar proton ATPase V-ATPase, large 900 kilodalton complex composed of peripheral V1 octamer A3B3CDE3FG3H hydrolyzing ATP at A-B interfaces and integral Vo domain a, c, c'', d, e, forming proton pore. Mechanism rotary: ATP hydrolysis in V1 drives rotation of central stalk D F and c-ring proteolipid assembling ten copies each

Ref: Forgac, Nature Reviews Mol Cell Biol, V-ATPase Structure and Lysosomal Acidification Function.

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