TY  - THES
A1  - Sharma, Tripti
T1  - Regulation of potassium channels in plants : biophysical mechanisms and physiological implacations
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Sharma, Tripti
A1  - Dreyer, Ingo
A1  - Riedelsberger, Janin
T1  - The role of K+ channels in uptake and redistribution of potassium in the model plant Arabidopsis thaliana
JF  - Frontiers in plant science
N2  - Potassium (K+) is inevitable for plant growth and development. It plays a crucial role in the regulation of enzyme activities, in adjusting the electrical membrane potential and the cellular turgor, in regulating cellular homeostasis and in the stabilization of protein synthesis. Uptake of K+ from the soil and its transport to growing organs is essential for a healthy plant development. Uptake and allocation of K+ are performed by K+ channels and transporters belonging to different protein families. In this review we summarize the knowledge on the versatile physiological roles of plant K+ channels and their behavior under stress conditions in the model plant Arabidopsis thaliana.
KW  - plant potassium channel
KW  - Shaker
KW  - TPK
KW  - K-ir-like
KW  - Arabidopsis thaliana
KW  - voltage-dependent
KW  - voltage-independent
Y1  - 2013
U6  - https://doi.org/10.3389/fpls.2013.00224
SN  - 1664-462X
VL  - 4
PB  - Frontiers Research Foundation
CY  - Lausanne
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  - Gajdanowicz, Pawel
A1  - Garcia-Mata, Carlos
A1  - Gonzalez, Wendy
A1  - Morales-Navarro, Samuel Elïas
A1  - Sharma, Tripti
A1  - Gonzalez-Nilo, Fernando Danilo
A1  - Gutowicz, Jan
A1  - Müller-Röber, Bernd
A1  - Blatt, Michael R.
A1  - Dreyer, Ingo
T1  - Distinct roles of the last transmembrane domain in controlling Arabidopsis K+ channel activity
N2  - The family of voltage-gated potassium channels in plants presumably evolved from a common ancestor and includes both inward-rectifying (K-in) channels that allow plant cells to accumulate K+ and outward-rectifying (K-out) channels that mediate K+ efflux. Despite their close structural similarities, the activity of Kin channels is largely independent of K+ and depends only on the transmembrane voltage, whereas that of K-out channels responds to the membrane voltage and the prevailing extracellular K+ concentration. Gating of potassium channels is achieved by structural rearrangements within the last transmembrane domain (S6). Here we investigated the functional equivalence of the S6 helices of the Kin channel KAT1 and the K-out channel SKOR by domain-swapping and site-directed mutagenesis. Channel mutants and chimeras were analyzed after expression in Xenopus oocytes. We identified two discrete regions that influence gating differently in both channels, demonstrating a lack of functional complementarity between KAT1 and SKOR. Our findings are supported by molecular models of KAT1 and SKOR in the open and closed states. The role of the S6 segment in gating evolved differently during specialization of the two channel subclasses, posing an obstacle for the transfer of the K+-sensor from K-out to K-in channels.
Y1  - 2009
UR  - http://www3.interscience.wiley.com/cgi-bin/issn?DESCRIPTOR=PRINTISSN&VALUE=0028-646X
U6  - https://doi.org/10.1111/j.1469-8137.2008.02749.x
SN  - 0028-646X
ER  -