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|Title:||Maize NPF6 proteins are homologs of Arabidopsis CHL1 that are selective for both nitrate and chloride|
|Other Titles:||NPF nitrate and chloride transport|
|Citation:||The Plant Cell, 2017; 29(9):00724|
|Publisher:||American Society of Plant Biologists|
|Zhengyu Wen, Stephen Tyerman, Julie Dechorgnat, Evgenia Ovchinnikova, Kanwarpal Dhugga, Brent N Kaiser|
|Abstract:||Nitrate uptake by plant cells requires both high and low-affinity transport activities. Arabidopsis (Arabidopsis thaliana, At) nitrate transporter 1/peptide transporter family (NPF) 6.3 is a dual-affinity plasma membrane transport protein that has both high and low-affinity functions. At-NPF6.3 imports and senses nitrate and is regulated by phosphorylation at Thr-101 (T101). A detailed functional analysis of two maize (Zea mays, Zm) homologs of At-NPF6.3 (Zm-NPF6.6 and Zm-NPF6.4) showed that Zm-NPF6.6 was a pH dependent non-biphasic high-affinity nitrate-specific transport protein. By contrast, maize NPF6.4 was a low-affinity nitrate transporter with efflux activity. When supplied chloride, NPF6.4 switched to a high-affinity chloride selective transporter, while NPF6.6 had only a low-affinity chloride transport activity. Structural predictions identified a nitrate binding His (H362) in NPF6.6 but not in NPF6.4. Mutation of NPF6.4 Tyr-370 to His (Y370H) resulted in saturable high-affinity nitrate transport activity and nitrate selectivity. Loss of H362 in NPF6.6 (H362Y) eliminated both nitrate and chloride transport. Furthermore, alterations to Thr-104, a conserved phosphorylation site in NPF6.6, resulted in a similar high-affinity nitrate transport activity with increased Km whereas equivalent changes in NPF6.4 (T106) disrupted high-affinity chloride transport activity. NPF6 proteins exhibit different substrate specificity in plants and regulate nitrate transport affinity/selectivity using a conserved His residue.|
|Keywords:||Arabidopsis; Zea mays; Chlorides; Nitrates; Anion Transport Proteins; Plant Proteins; Gene Expression Regulation, Plant|
|Rights:||© 2017 American Society of Plant Biologists. All rights reserved.|
|Appears in Collections:||Biochemistry publications|
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