title: Effects of delipidation on proton translocation and ATPase activity in beef heart electron transport particles.
abstract: Delipidation of beef heart electron transport particles with phospholipase A2 has been examined. When the particles were treated with the lipase and subjected to a low bovine serum albumin wash, ATPase activity was unaffected as was the lipid/protein ratio of the particles. However, energisation by ATP/Mg2+ was abolished. Furthermore, unsaturated but not saturated fatty acids discharged the steady-state ATP-driven membrane potential of control samples. When the phospholipase A2 hydrolysis products were removed, inhibition of energy-linked reactions in the lipid-depleted particles was still observed and was interpreted in terms of non-specific leaks in the vesicle membranes, and 'specific' leaks through impaired H+-ATPase complexes. ATPase activity was less susceptible to delipidation than energisation but was, nevertheless, strongly inhibited at 50 percent lipid depletion. Spin label studies indicated a decrease in the fluidity of particle membranes accompanying delipidation. Moreover, the discontinuity seen in Arrhenius plots of ATPase activity was shifted from 17 degrees C (control) to 22 degrees C at 50 percent phospholipid depletion. The data are consistent with a release of unsaturated fatty acids by phospholipase A2 rendering the transport particles both leakier and the membranes less fluid than controls.
mesh_terms: D000818:Animals; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport / Q000187:drug effects*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D010740:Phospholipases / Q000494:pharmacology*; D010741:Phospholipases A / Q000378:metabolism / Q000494:pharmacology*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011522:Protons
chemical_list: D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids; D011522:Protons; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D006180:Proton-Translocating ATPases