An Escherichia coli homologue of eukaryotic potassium channel proteins.

Abstract

A DNA sequence in Eschenchia coil K-12 contais an evident gene, kch, which predicts a protein 417 residues long with extensive simii to a group of eukaryotic potassium channel proteins in amino acid sequence, in the presence ofsix apparent tmembrane (S) The molecular ancestry of eukaryotic voltage-gated cation channels is obscure, beyond the likelihood that a potassium channel came first. This likelihood is based on the similarity between potassium channel proteins and other cation channel proteins in a set of six transmembrane domains with a cation-specific pore located between the fifth and sixth domains. While potassium channel proteins contain no more than one such set of domains, sodium and calcium channel proteins contain four sets in linear order, implying a history of two duplication events (1). Here

Multiple Genes, Tissue Specificity, and Expression-Dependent Modulation Contribute to the Functional Diversity of Potassium Channels in Arabidopsis thaliana

“…This new sequence shows a region with six putative transmembrane domains and a K + -selective pore sequence (H5) between the fifth and sixth domains. These two sequence characteristics have previously been used as sufficient evidence to predict newly sequenced cDNAs as encoding K + channels (Milkman, 1994). Furthermore, the AKT2 sequence shows highest similarity to the two known K + channel clones KAT1 and AKT1 (59-63% identity).…”

A prokaryotic potassium ion channel with two predicted transmembrane segments from Streptomyces lividans.

“…So far it is not known whether this gene is functional (Milkman, 1994). The alignment of its deduced amino acids reveals that its deduced H5 segment is most closely related to those within IRKs (Figures 8 and 9), whereas the transmembrane segments (MI and M2, S5 and S6) from various eukaryotic channels, as well as KcsA from S.lividans, share only a few identical amino acids or none at all with Kch from E.coli.…”

“…in muscle cells (Petrou etal., 1995). Various K+ ion channels from different eukaryotes have been analysed after the translation of the corresponding mRNA within oocytes (for a review, see Hille, 1992 , KSC1, ShCl (Pongs et al, 1988), Slo (Atkinson et al, 1991), Kch (Milkman, 1994) and ROMK1 (Ho et al, 1993) proteins.…”

A prokaryotic perspective on pentameric ligand-gated ion channel structure

“…The first glimpse of hope was seen in 1994, when the first bacterial K + -channel was discovered [134] , followed four years later by the first high-resolution structure of any ion channel solved in the laboratory of Roderick MacKinnon [135] .…”