EVIDENCE THAT PLANT K+ CHANNEL PROTEINS HAVE 2 DIFFERENT TYPES OF SUBUNITS

Plant K+ channel proteins have been previously characterized as tetram ers of membrane-spanning alpha subunit polypeptides. Recent studies ha ve identified a 39-kD, hydrophilic polypeptide that is a structural co mponent of purified animal K+ channel proteins. We have cloned and seq uenced an Arabidopsis thaliana cDNA encoding a 38.4-kD polypeptide tha t has a sequence homologous to the animal K+ channel beta subunit. Sou thern and northern analyses indicate the presence of a gene encoding t his cDNA in the Arabidopsis genome and that its transcription product is present in Arabidopsis cells. To our knowledge, this is the first r eport to document the presence of K+ channel beta subunits in plants.