NDLI: Extracellular Glucose Increases the Coupling Capacity of the Yeast V H+-ATPase and the Resistance of Its H+ Transport Activity to Nitrate Inhibition

Content Provider	PubMed Central
Author	Ribeiro, Camila C. Monteiro, Renan M. Freitas, Flavia P. Retamal, Claudio Teixeira, Layz R. S. Palma, Livia M. Silva, Flavia E. Façanha, Arnoldo R. Okorokova-façanha, Anna L. Okorokov, Lev A.
Editor	Permyakov, Eugene A.
Copyright Year	2012
Abstract	V H+-ATPase has an important role in a variety of key physiological processes. This enzyme is reversibly activated/partly inactivated by the addition/exhaustion of extracellular glucose. The current model of its regulation assumes the reversible disassembly/reassembly of ∼60–70% of the V1 and V0 membrane complexes, which are responsible for ATP hydrolysis and H+ conductance, respectively. The number of assembled complexes determines the pump activity because disassembled complexes are inactive. The model predicts the identical catalytic properties for the activated and semi-active enzymes molecules. To verify the model predictions we have isolated total membranes from yeast spheroplasts that were pre-incubated either with or without glucose. Nitrate treatment of membranes revealed the similar ATPase inhibition for two enzyme states, suggesting that they have identical structures that are essential for ATP hydrolysis. However, H+ transport was inhibited more than the ATPase activities, indicating a nitrate uncoupling action, which was significantly higher for the nonactivated enzyme. This finding suggests that the structure of the non-activated enzyme, which is essential for H+ transport, is less stable than that of the activated enzyme. Moreover, the glucose activation of the pump increases i) its coupling capacity; ii) its KM for ATP hydrolysis and ATP affinity for H+ transport; iii) the Vmax for H+ transport in comparison with the Vmax for ATP hydrolysis and iv) the immune reactivity of catalytic subunit A and regulatory subunit B by 9.3 and 2.4 times, respectively. The protein content of subunits A and B was not changed by extracellular glucose. We propose that instead of the dissociation/reassociation of complexes V1 and V0, changes in the extracellular glucose concentration cause reversible and asymmetrical modulations in the immune reactivity of subunits A and B by their putative biochemical modifications. This response asymmetrically modulates H+-transport and ATP hydrolysis, exhibiting distinct properties for the activated versus non-activated enzymes.
Related Links	http://dx.doi.org/10.1371/journal.pone.0049580
Starting Page	49580
File Format	PDF
ISSN	19326203
e-ISSN	19326203
Journal	PLoS ONE
Issue Number	11
Volume Number	7
Language	English
Publisher	Public Library of Science
Publisher Date	2012-11-01
Access Restriction	Open
Rights Holder	Public Library of Science
Subject Keyword	Biochemistry, Genetics and Molecular Biology(all) Agricultural and Biological Sciences(all) Medicine(all) Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Multidisciplinary

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