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J Gen Physiol. 2019 Feb 4;151(2):258-263. doi: 10.1085/jgp.201812260. Epub 2019 Jan 8.

Reinterpretation of the substrate specificity of the voltage-sensing phosphatase during dimerization.

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Department of Biology and Program in Neuroscience, Bates College, Lewiston, ME.
Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT.
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA


Voltage-sensing phosphatases (VSPs) cleave both 3- and 5-phosphates from inositol phospholipids in response to membrane depolarization. When low concentrations of Ciona intestinalis VSP are expressed in Xenopus laevis oocytes, the 5-phosphatase reaction can be observed during large membrane depolarizations. When higher concentrations are expressed, the 5-phosphatase activity is observed with smaller depolarizations, and the 3-phosphatase activity is revealed with strong depolarization. Here we ask whether this apparent induction of 3-phosphatase activity is attributable to the dimerization that has been reported when VSP is expressed at higher concentrations. Using a simple kinetic model, we show that these enzymatic phenomena can be understood as an emergent property of a voltage-dependent enzyme with invariant substrate selectivity operating in the context of endogenous lipid-metabolizing enzymes present in oocytes. Thus, a switch of substrate specificity with dimerization need not be invoked to explain the appearance of 3-phosphatase activity at high VSP concentrations.

[Available on 2019-08-04]

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