AtKCO3 is the only putative voltage-independent K+ channel subunit of Arabidopsis thaliana with a single permeation pore domain. We show that overexpressed AtKCO3 or AtKCO3::GFP proteins are efficiently sorted to the tonoplast, but vacuoles isolated from these transgenic plants do not have significant alterations in current density. Consistently, analysis of KCO3 knockout plants did not reveal marked growth alterations. Because the permeation pore of K+ channels is formed by four copies of the pore domain, we have investigated whether KCO3 assembles into tetramers. Upon velocity gradient centrifugation, both AtKCO3 and AtKCO3::GFP were detected as homodimers, an assembly state that therefore would not allow for activity. We conclude that if AtKCO3 functions as a K+ channel, active tetramers are either held by particularly weak interactions, different from those that allow dimer formation, or are assembled only under unknown, specific physiological conditions. Supported by EU Marie Curie RTN 'Vacuolar Transport Equipment for Growth Regulation in Plants' (MRTN-CT-2006-035833) and by the 2008 PRIN Program.
The enigmatic, putative potassium channel AtKCO3 of Arabidopsis tonoplast
ScholzStarke J;Carpaneto A;Vitale A;Pedrazzini E
2012
Abstract
AtKCO3 is the only putative voltage-independent K+ channel subunit of Arabidopsis thaliana with a single permeation pore domain. We show that overexpressed AtKCO3 or AtKCO3::GFP proteins are efficiently sorted to the tonoplast, but vacuoles isolated from these transgenic plants do not have significant alterations in current density. Consistently, analysis of KCO3 knockout plants did not reveal marked growth alterations. Because the permeation pore of K+ channels is formed by four copies of the pore domain, we have investigated whether KCO3 assembles into tetramers. Upon velocity gradient centrifugation, both AtKCO3 and AtKCO3::GFP were detected as homodimers, an assembly state that therefore would not allow for activity. We conclude that if AtKCO3 functions as a K+ channel, active tetramers are either held by particularly weak interactions, different from those that allow dimer formation, or are assembled only under unknown, specific physiological conditions. Supported by EU Marie Curie RTN 'Vacuolar Transport Equipment for Growth Regulation in Plants' (MRTN-CT-2006-035833) and by the 2008 PRIN Program.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
