Plant K+ channel alpha-subunits assemble indiscriminately.
In plants a large diversity of inwardly rectifying K+ channels (K(in) channels) has been observed between tissues and species. However, only three different types of voltage-dependent plant K+ uptake channel subfamilies have been cloned so far; they relate either to KAT1, AKT1, or AtKC1. To explore the mechanisms underlying the channel diversity, we investigated the assembly of plant inwardly rectifying alpha-subunits. cRNA encoding five different K+ channel alpha-subunits of the three subfamilies (KAT1, KST1, AKT1, SKT1, and AtKC1) which were isolated from different tissues, species, and plant families (Arabidopsis thaliana and Solanum tuberosum) was reciprocally co-injected into Xenopus oocytes. We identified plant K+ channels as multimers. Moreover, using K+ channel mutants expressing different sensitivities to voltage, Cs+, Ca2+, and H+, we could prove heteromers on the basis of their altered voltage and modulator susceptibility. We discovered that, in contrast to animal K+ channel alpha-subunits, functional aggregates of plant K(in) channel alpha-subunits assembled indiscriminately. Interestingly, AKT-type channels from A. thaliana and S. tuberosum, which as homomers were electrically silent in oocytes after co-expression, mediated K+ currents. Our findings suggest that K+ channel diversity in plants results from nonselective heteromerization of different alpha-subunits, and thus depends on the spatial segregation of individual alpha-subunit pools and the degree of temporal overlap and kinetics of expression.
Dreyer
I
I
Institut für Biophysik, Universität Hannover, Germany.
Antunes
S
S
Hoshi
T
T
Müller-Röber
B
B
Palme
K
K
Pongs
O
O
Reintanz
B
B
Hedrich
R
R
D029681:Arabidopsis Proteins; D001704:Biopolymers; D004594:Electrophysiology; D007700:Kinetics; D008564:Membrane Potentials; D010940:Plant Proteins / Q000502:physiology; D010944:Plants; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D013045:Species Specificity
D029681:Arabidopsis Proteins; D001704:Biopolymers; C501210:KAT1 protein, Arabidopsis; D010940:Plant Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C074500:AKT1 protein, Arabidopsis