Cloning and expression of cDNA and genomic clones encoding three delayed rectifier potassium channels in rat brain

Rat brain cDNA and genomic clones encoding three K + channels, K v1, K v2, and K v3, have been isolated by screening with Shaker probes and encode proteins of 602, 530, and 525 amino acids. Each of the deduced protein sequences contains six hydrophobic domains (including an S4-type region characteristic of many voltage-gated channels) and are 68%–72% identical to each other overall. Transcripts of ∼3.5, ∼6.5, and ∼9.5 kb encode K v1, K v2, and K v3, respectively. The K v2, mRNA is expressed only in brain, whereas the K v1 and K v3, transcripts are found in several other tissues as well. There is a marked increase in the amount of K v1 mRNA in cardiac tissue during development and a similar, but less pronounced, increase of both this mRNA and the K v2, transcript in brain. RNAs synthesized in vitro from the three clones induce voltage- and time-dependent, delayed rectifier-like K + currents when injected into Xenopus oocytes, demonstrating that they encode functional K + channels.