Evidence of differential pH regulation of the  Arabidopsis  vacuolar Ca 2+ /H +  antiporters CAX1 and CAX2 | Zendy

Pittman Jon K. | Zendy; Shigaki Toshiro | Zendy; Hirschi Kendal D. | Zendy

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Evidence of differential pH regulation of the Arabidopsis vacuolar Ca 2+ /H + antiporters CAX1 and CAX2

Author(s) -

Pittman Jon K.,

Shigaki Toshiro,

Hirschi Kendal D.

Publication year - 2005

Publication title -

febs letters

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.593

H-Index - 257

eISSN - 1873-3468

pISSN - 0014-5793

DOI - 10.1016/j.febslet.2005.03.085

Subject(s) - antiporters , antiporter , vacuole , cytosol , arabidopsis , transporter , biochemistry , ion transporter , vesicle , chemistry , membrane transport , biophysics , transport protein , biology , cytoplasm , membrane , gene , enzyme , mutant

The Arabidopsis Ca 2+ /H + antiporters cation exchanger (CAX) 1 and 2 utilise an electrochemical gradient to transport Ca 2+ into the vacuole to help mediate Ca 2+ homeostasis. Previous whole plant studies indicate that activity of Ca 2+ /H + antiporters is regulated by pH. However, the pH regulation of individual Ca 2+ /H + antiporters has not been examined. To determine whether CAX1 and CAX2 activity is affected by pH, Ca 2+ /H + antiport activity was measured in vacuolar membrane vesicles isolated from yeast heterologously expressing either transporter. Ca 2+ transport by CAX1 and CAX2 was regulated by cytosolic pH and each transporter had a distinct cytosolic pH profile. Screening of CAX1/CAX2 chimeras identified an amino acid domain within CAX2 that altered the pH‐dependent Ca 2+ transport profile so that it was almost identical to the pH profile of CAX1. Results from mutagenesis of a specific His residue within this domain suggests a role for this residue in pH regulation.

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