Potassium and sodium transport in non-animal cells: the Trk/Ktr/HKT transporter family 

 -  Cellular and Molecular Life Sciences, 67(15), p.2511-2532, 2010 .
<br/><br/> Bacterial Trk and Ktr, fungal Trk and plant HKT form a family of membrane transporters permeable to K? and/or Na? and characterized by a common structure probably derived from an ancestral K? channel subunit. This transporter family, specific of non-animal cells, displays a large diversity in terms of ionic permeability, affinity and energetic coupling (H?-K? or Na?-K? symport, K? or Na? uniport), which might reflect a high need for adaptation in organisms living in fluctuating or dilute environments. Trk/Ktr/HKT transporters are involved in diverse functions, from K? or Na? uptake to membrane potential control, adaptation to osmotic or salt stress, or Na? recirculation from shoots to roots in plants. Structural analyses of bacterial Ktr point to multimeric structures physically interacting with regulatory subunits. Elucidation of Trk/Ktr/HKT protein structures along with characterization of mutated transporters could highlight functional and evolutionary relationships between ion channels and transporters displaying channel-like features.