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, Golgi, secretory vesicles and plasma membrane of intercalated cells, acidifying lumen to pH 4.5 to 5.5 required for activation of acid hydrolases, ligand-receptor dissociation, proprotein processing and secondary transport driven by H+ gradient. Inhibition by bafilomycin and concanamycin abolishes acidification, blocks lysosomal degradation and bone resorption by osteoclasts. Na+/K+ ATPase and CFTR do not mediate lysosomal acidification, highlighting V-type specialization for compartmental pH control. Such detailed mechanistic insight is frequently examined in competitive tests including NEET, CUET, CSIR-NET and GATE where transporter classification, energetics and disease linkage are integrated into problem-solving questions.
Ref: Forgac, Nat Rev Mol Cell Biol 2007, Vacuolar H+-ATPases; Alberts, 7th ed., Chapter 13 acidification.