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Cytochemical Localization of ATPase Activity in Oat Roots Localizes a Plasma Membrane-Associated Soluble Phosphatase, Not the Proton Pump

Cytochemical Localization of ATPase Activity in Oat Roots Localizes a Plasma Membrane-Associated... Abstract Cytochemical techniques employing lead-precipitation of enzymically released inorganic phosphate have been widely used in attempts to localize the plasma membrane proton pump (H+-ATPase) in electron micrographs. Using Avena sativa root tissue we have performed a side-by-side comparison of ATPase activity observed in electron micrographs with that observed in in vitro assays using ATPases found in the soluble and plasma membrane fractions of homogenates. Cytochemical analysis of oat roots, which had been fixed in glutaraldehyde in order to preserve subcellular structures, identifies an ATPase located at or near the plasma membrane. However, the substrate specificity and inhibitor sensitivity of the in situ localized ATPase appear identical to those of an in vitro ATPase activity found in the soluble fraction, and are completely unlike those of the plasma membrane proton pump. Further studies demonstrated that the plasma membrane H+-ATPase is particularly sensitive to inactivation by the fixatives glutaraldehyde and formaldehyde and by lead. In contrast, the predominant soluble ATPase activity in oat root homogenates is less sensitive to fixation and is completely insensitive to lead. Based on these results, we propose a set of criteria for evaluating whether a cytochemically localized ATPase activity is, in fact, due to the plasma membrane proton pump. 1 Supported by grants to M. R. S. from the Department of Energy (No. DE-AC0283ER13086) and to the College of Agriculture and Life Sciences (Hatch Project No. 1757) and to R. R. E. from the National Science Foundation (No. PCM 83-12442). This content is only available as a PDF. © 1988 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Physiology Oxford University Press

Cytochemical Localization of ATPase Activity in Oat Roots Localizes a Plasma Membrane-Associated Soluble Phosphatase, Not the Proton Pump

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References (10)

Publisher
Oxford University Press
Copyright
Copyright © 2021 American Society of Plant Biologists
ISSN
0032-0889
eISSN
1532-2548
DOI
10.1104/pp.86.3.841
Publisher site
See Article on Publisher Site

Abstract

Abstract Cytochemical techniques employing lead-precipitation of enzymically released inorganic phosphate have been widely used in attempts to localize the plasma membrane proton pump (H+-ATPase) in electron micrographs. Using Avena sativa root tissue we have performed a side-by-side comparison of ATPase activity observed in electron micrographs with that observed in in vitro assays using ATPases found in the soluble and plasma membrane fractions of homogenates. Cytochemical analysis of oat roots, which had been fixed in glutaraldehyde in order to preserve subcellular structures, identifies an ATPase located at or near the plasma membrane. However, the substrate specificity and inhibitor sensitivity of the in situ localized ATPase appear identical to those of an in vitro ATPase activity found in the soluble fraction, and are completely unlike those of the plasma membrane proton pump. Further studies demonstrated that the plasma membrane H+-ATPase is particularly sensitive to inactivation by the fixatives glutaraldehyde and formaldehyde and by lead. In contrast, the predominant soluble ATPase activity in oat root homogenates is less sensitive to fixation and is completely insensitive to lead. Based on these results, we propose a set of criteria for evaluating whether a cytochemically localized ATPase activity is, in fact, due to the plasma membrane proton pump. 1 Supported by grants to M. R. S. from the Department of Energy (No. DE-AC0283ER13086) and to the College of Agriculture and Life Sciences (Hatch Project No. 1757) and to R. R. E. from the National Science Foundation (No. PCM 83-12442). This content is only available as a PDF. © 1988 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Journal

Plant PhysiologyOxford University Press

Published: Mar 1, 1988

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