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A Plant Homolog of Animal Glutamate Receptors Is an Ion Channel Gated by Multiple Hydrophobic Amino Acids

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Science Signaling  11 Jun 2013:
Vol. 6, Issue 279, pp. ra47
DOI: 10.1126/scisignal.2003762

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Ionotropic Amino Acid Sensor

Sequence similarity suggests that there are plant homologs of animal ionotropic glutamate receptors, which are ligand-gated, glutamate-activated ion channels. Tapken et al. showed that the Arabidopsis homolog AtGLR1.4 behaved as anything but a glutamate-activated channel. Of the 20 amino acids tested on AtGLR1.4 expressed in Xenopus oocytes, methionine was the most effective and potent of the seven amino acids that activated the channel, arginine was the most effective competitive antagonist of methionine-activated current, and glutamate did not affect channel activity. Electrophysiological analysis showed that AtGLR1.4 was a nonselective cation channel. Analysis of leaves from knockout plants indicated that AtGLR1.4 mediated membrane depolarization in response to methionine but not glutamate. Thus, to call these glutamate receptors in plants is a misnomer.

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