Q.23 In the enzyme ATP synthase Fo domain is sensitive to
The Fo domain of ATP synthase is sensitive to oligomycin. This macrolide antibiotic specifically binds the c-subunit ring in the Fo proton channel, blocking H⁺ translocation through the membrane and halting ATP synthesis without affecting F1 ATPase activity.
Option Analysis
-
(1) Oligophycin: Incorrect—nonexistent compound; likely misspelling distractor.
-
(2) Oligosaccharide: Carbohydrates (e.g., maltose); no interaction with membrane protein complexes.
-
(3) Oligomycin: Correct—binds Fo c-ring (subunits c9-15), inhibits proton flow stoichiometrically. Classic tool for oxidative phosphorylation studies.
-
(4) Oligonucleotide: Short ssDNA/RNA; nucleic acids unrelated to mitochondrial bioenergetics.
Answer: (3) Oligomycin.
Introduction to ATP Synthase Inhibition
In the enzyme ATP synthase Fo domain is sensitive to oligomycin, which blocks the proton-translocating c-ring channel. This specifically uncouples proton motive force from ATP synthesis, making oligomycin essential for dissecting respiratory chain function.
Oligomycin Binding Mechanism
-
Target: Hydrophobic macrolide penetrates Fo membrane sector
-
Action: Occludes c-subunit proton pore, preventing 3H⁺/ATP rotation
-
Effect: Δψ maintained, O₂ consumption halted, ATP/ADP ratio drops
Distinguishing Other Oligo- Terms
| Compound | Class | ATP Synthase Effect |
|---|---|---|
| Oligomycin | Antibiotic | Fo blocker |
| Oligosaccharide | Carb | None |
| Oligonucleotide | Nucleic acid | None |
| Oligophycin | Fake | None |
GATE Biochemistry Application
Tests ETC inhibitor specificity:
-
Oligomycin: Fo (ATP synthase)
-
Cyanide: Complex IV
-
Rotenone: Complex I
Critical for mitochondrial bioenergetics, OXPHOS pathway questions.
