Potassium channels from NG108‐15 neuroblastoma‐glioma hybrid cells

Abstract

The complete amino acid sequences of two potassium channel proteins from NGlOE-15 neuroblastoma-glioma hybrid cells have been deduced by cloning and sequencing the cDNAs. One of these proteins (NGKZ) is structurally more closely related to the Drosophila Show gene product than to the Shaker and Shah gene products, whereas the other (NGKl) is identical with a rat brain potassium channel protein (BK2) which is more closely related to the Drosophila Shaker gene product. mRNAs derived from both the cloned cDNAs, when injected into Xenopus oocytes, direct the formation of functional potassium channels with properties of delayed rectifiers.

Slow inactivation conserved in heteromultimeric voltage‐dependent K+ channels between Shaker (Kv1) and Shaw (Kv3) subfamilies

“…IA) and -20 mY for NGK2 channels (Fig. IB) in oocytes, as described previously [4,13,18,22]. Subconductance states are frequently observed in NGKI homomultimeric channels but are very rare in NGK2 homomultimeric channels (Fig.…”

“…Oocytes were harvested from adult Xenopus laevis, and the vitelline envelopes were peeled off under a dissecting microscope 2-3 h before starting electrophysiologlcal recording NGKI (Kvl.2)-and NGK2 (K v3.1a)-speclfic mRNAs were synthesized m vitro, using XhoI-c1eaved pSPNGKI and pSPNGK2, respectively [22]. TranscriptIOn was primed *Correspondmg author.…”

“…Heteromultimeric K+ channels can be formed by K+ channel proteins belonging to the same subfamilies [1, 6,16.19], but not between ones belonging to different subfamilies [20,21]. However, in oocytes injected with a mixture ofmRNAs encoding rat Shaker NGKI (Kv1.2) and mouse Shall' NGK2 (Kv3.1a) K+ channels [22], a whole-cell outward current which cannot be explained by a simple sum of NGKI and NGK2 current components has been recorded [7]. This suggests that proteins of NGKI and NGK2 voltage-dependent K+ channels, belonging to different subfamilies, form heteromultimers [7].…”

A mouse brain homolog of the Drosophila Shab K+ channel with conserved delayed-rectifier properties

“…These properties contrast with those of mShab1 and jShab, which have slow activation of macroscopic current and are insensitive to 4-AP. Even a mammalian homolog of Drosophila Shaw that has been expressed (Yokoyama et al, 1989) activates at a rate that is considerably faster than either mShab1 orf;rhab. The current-voltage relation of this mammalian Shaw homolog also differs from Shab currents in that it is considerably shifted to depolarized voltages.…”

“…Each Drosophila gene, Shaker, Shab, Shaw, and Shal, is conserved in mammals (Baumann et al, 1988;Tempel et al, 1988;Frech et al, 1989;Yokoyama et al, 1989;Wei et al, 1990) where some are present as multigene subfamilies.…”