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Biophys. J. BioFAST: First Published August 18, 2006. doi:10.1529/biophysj.106.091777
© 2006 by the Biophysical Society.

A more recent version of this article appeared on November 15, 2006.
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CHANNELS, RECEPTORS, AND ELECTRICAL SIGNALING

Stoichiometry studies reveal functional properties of KDC1 in plant Shaker potassium channels

Alessia Naso 1, Roberta Montisci 1, Franco Gambale 1 and Cristiana Picco 1*

1 Istituto di Biofisica, CNR

* To whom correspondence should be addressed. E-mail: picco{at}ge.ibf.cnr.it.

Submitted on June 20, 2006
Revised on July 19, 2006
Accepted on 3 August 2006


  Abstract
Functional heteromeric plant Shaker potassium channels can be formed by the assembly of subunits from different tissues, as well as from diverse plant species. KDC1 (K+ Daucus carota 1) produces inward-rectifying currents in Xenopus oocytes when coexpressed with KAT1 and other subunits appertaining to different plant Shaker subfamilies. Owing to the presence of KDC1, resulting heteromeric channels display slower activation kinetics, a shift of the activation threshold towards more negative membrane potentials and current potentiation upon the addition of external zinc. Despite available information on heteromerization of plant Shaker channels, very little is known to date on the properties of the various stoichiometric configurations formed by different subunits. In order to investigate the functional properties of heteromeric nKDC1/mKAT1 configurations, we realized a series of dimeric constructs combining KDC1 and KAT1 {alpha}-subunits. We found that homomeric channels formed by monomeric or dimeric {alpha}-subunit constructs show identical biophysical characteristics. Coinjections of diverse tandem constructs, instead, displayed significantly different currents proving that KDC1 has high affinity for KAT1 and participates to the formation of functional channels with at most 2 KDC1 subunits, whereas 3 KDC1 subunits prevented the formation of functional channels. This paper brings a contribution to the understanding of the molecular mechanisms regulating plant Shaker channel functionality by association of modulatory subunits.

Key Words: Shaker potassium channels, dimeric construct, plants, stoichiometry




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C. Picco, A. Naso, P. Soliani, and F. Gambale
The Zinc Binding Site of the Shaker Channel KDC1 from Daucus carota
Biophys. J., January 15, 2008; 94(2): 424 - 433.
[Abstract] [Full Text] [PDF]


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Copyright © 2006 by the Biophysical Society.