TY  - JOUR
A1  - Poree, Fabien
A1  - Wulfetange, K.
A1  - Naso, A.
A1  - Carpaneto, Armando
A1  - Roller, A.
A1  - Natura, G.
A1  - Bertl, Adam
A1  - Sentenac, H.
A1  - Thibaud, Jean-Baptiste
A1  - Dreyer, Ingo
T1  - Plant K-in and K-out channels : Approaching the trait of opposite rectification by analyzing more than 250 KAT1- SKOR chimeras
N2  - Members of the Shaker-like plant K+ channel family share a common structure, but are highly diverse in their function: they behave as either hyperpolarization-activated inward-rectifying (K-in) channels, or leak-like (K-weak) channels, or depolarization-activated outward-rectifying (K-out) channels. Here we created 256 chimeras between the K-in channel KAT1 and the K-out channel SKOR. The chimeras were screened in a potassium-uptake deficient yeast strain to identify those, which mediate potassium inward currents, i.e., which are functionally equivalent to KAT1. This strategy allowed Lis to identify three chimeras which differ from KAT1 in three parts of the polypeptide: the cytosolic N- terminus, the cytosolic C-terminus, and the putative voltage-sensor S4. Additionally, mutations in the K-out Channel SKOR were generated in order to localize molecular entities underlying its depolarization activation. The triple mutant SKOR-D312N-M313L-1314G, carrying amino-acid changes in the S6 segment, was identified as a channel which did not display any rectification in the tested voltage-range. (C) 2005 Elsevier Inc. All rights reserved
Y1  - 2005
SN  - 0006-291X
ER  - 
TY  - JOUR
A1  - Rocchetti, Alessandra
A1  - Sharma, Tripti
A1  - Wulfetange, Camilla
A1  - Scholz-Starke, Joachim
A1  - Grippa, Alexandra
A1  - Carpaneto, Armando
A1  - Dreyer, Ingo
A1  - Vitale, Alessandro
A1  - Czempinski, Katrin
A1  - Pedrazzini, Emanuela
T1  - The putative K+ channel subunit AtKCO3 forms stable dimers in arabidopsis
JF  - Frontiers in plant science
N2  - The permeation pore of K+ channels is formed by four copies of the pore domain. AtKCO3 is the only putative voltage-independent K+ channel subunit of Arabidopsis thaliana with a single pore domain. KCO3-like proteins recently emerged in evolution and, to date, have been found only in the genus Arabidopsis (A. thaliana and A. lyrata). We show that the absence of KCO3 does not cause marked changes in growth under various conditions. Only under osmotic stress we observed reduced root growth of the kco3-1 null-allele line. This phenotype was complemented by expressing a KCO3 mutant with an inactive pore, indicating that the function of KCO3 under osmotic stress does not depend on its direct ability to transport ions. Constitutively overexpressed AtKCO3 or AtKCO3::G FP are efficiently sorted to the tonoplast indicating that the protein is approved by the endoplasmic reticulum quality control. However, vacuoles isolated from transgenic plants do not have significant alterations in current density. Consistently, both AtKCO3 and AtKCO3::GFP are detected as homodimers upon velocity gradient centrifugation, an assembly state that would not allow for activity. We conclude that if AtKCO3 ever functions as a K+ channel, active tetramers are held by particularly weak interactions, are formed only in unknown specific conditions and may require partner proteins.
KW  - Arabidopsis
KW  - membrane proteins
KW  - potassium channels
KW  - protein assembly
KW  - tonoplast
Y1  - 2012
U6  - https://doi.org/10.3389/fpls.2012.00251
SN  - 1664-462X
VL  - 3
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Becker, Dirk
A1  - Geiger, D.
A1  - Dunkel, M.
A1  - Roller, A.
A1  - Bertl, Adam
A1  - Latz, A.
A1  - Carpaneto, Armando
A1  - Dietrich, Peter
A1  - Roelfsema, M. R. G.
A1  - Voelker, C.
A1  - Schmidt, D.
A1  - Müller-Röber, Bernd
A1  - Czempinski, Katrin
A1  - Hedrich, R.
T1  - AtTPK4, an Arabidopsis tandem-pore K+ channel, poised to control the pollen membrane voltage in a pH- and Ca2+- dependent manner
N2  - The Arabidopsis tandem-pore K+ (TPK) channels displaying four transmembrane domains and two pore regions share structural homologies with their animal counterparts of the KCNK family. In contrast to the Shaker-like Arabidopsis channels (six transmembrane domains/one pore region), the functional properties and the biological role of plant TPK channels have not been elucidated yet. Here, we show that AtTPK4 (KCO4) localizes to the plasma membrane and is predominantly expressed in pollen. AtTPK4 (KCO4) resembles the electrical properties of a voltage-independent K+ channel after expression in Xenopus oocytes and yeast. Hyperpolarizing as well as depolarizing membrane voltages elicited instantaneous K+ currents, which were blocked by extracellular calcium and cytoplasmic protons. Functional complementation assays using a K+ transport-deficient yeast confirmed the biophysical and pharmacological properties of the AtTPK4 channel. The features of AtTPK4 point toward a role in potassium homeostasis and membrane voltage control of the growing pollen tube. Thus, AtTPK4 represents a member of plant tandem-pore-K+ channels, resembling the characteristics of its animal counterparts as well as plant-specific features with respect to modulation of channel activity by acidosis and calcium
Y1  - 2004
SN  - 0027-8424
ER  -