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Protease- and Acid-catalyzed Labeling Workflows Employing 18O-enriched Water
Published on: February 20, 2013
Oxygen-17 appears only in protein in water-stressed soybean leaves labeled by (17)O2
Terry Gullion1, Tsyr-Yan Yu, Manmilan Singh
1Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, USA.
Abstract:
We have used a rotational-echo adiabatic-passage double-resonance (13)C{(17)O} solid-state NMR experiment to prove that the glycine produced in the oxygenase reaction of ribulose bisphosphate carboxylase-oxygenase is incorporated exclusively into protein (or protein precursors) of intact, water-stressed soybean leaves exposed to (13)CO(2) and (17)O(2). The water stress increased stomatal resistance and decreased gas exchange so that the Calvin cycle in the leaf chloroplasts was no more than 35% (13)C isotopically enriched. Labeled O(2) levels were sufficient, however, to increase the (17)O isotopic concentration of oxygenase products 20-fold over the natural-abundance level of 0.04%. The observed direct incorporation of glycine into protein shows that water stress suppresses photorespiration in soybean leaves.
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