A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel.
Plant high-affinity K(+) transport (HKT) proteins are so named because of their relation to bacterial and fungal transporters that mediate high-affinity K(+) uptake. The view that HKT family members are sodium-selective uniporters or sodium-potassium symporters is widely held. We have found that one of the rice HKT proteins also functions as a Ca(2+)-permeable cation channel that conducts current carried by a wide range of monovalent and divalent cations. The HKT rice gene, named OsHKT2;4, is expressed in several cell types, including root hairs and vascular parenchyma cells. The protein is localized to the plasma membrane, thereby providing a mechanism for cation uptake and extrusion. This finding goes against firmly entrenched dogma in showing that HKT proteins can function as both ion carriers and channels. The study further extends the function of HKT proteins to Ca(2+)-linked processes and, in so doing, defines a previously undescribed type of Ca(2+)-permeable cation channels in plants. The work also raises questions about the evolutionary changes in this protein family following the divergence of monocots and dicots.
Lan
Wen-Zhi
WZ
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
Wang
Wei
W
Wang
Suo-Min
SM
Li
Le-Gong
LG
Buchanan
Bob B
BB
Lin
Hong-Xuan
HX
Gao
Ji-Ping
JP
Luan
Sheng
S
D000818:Animals; D002118:Calcium / Q000737:chemistry; D015220:Calcium Channels / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000737:chemistry; D002412:Cations / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D007473:Ion Channels / Q000737:chemistry; D007700:Kinetics; D008954:Models, Biological; D009865:Oocytes / Q000378:metabolism; D012275:Oryza / Q000378:metabolism*; D010641:Phenotype; D011188:Potassium / Q000737:chemistry*; D015222:Sodium Channels / Q000378:metabolism*; D027981:Symporters / Q000378:metabolism; D014981:Xenopus
D015220:Calcium Channels; D027682:Cation Transport Proteins; D002412:Cations; D007473:Ion Channels; D015222:Sodium Channels; D027981:Symporters; D011188:Potassium; D002118:Calcium