title: Identification of a novel bacterial K(+) channel.
abstract: In an attempt to explore unknown K(+) channels in mammalian cells, especially ATP-sensitive K(+) (K(ATP)) channels, we compared the sequence homology of Kir6.1 and Kir6.2, two pore-forming subunits of mammalian K(ATP) channel genes, with bacterial genes that code for selective proteins with confirmed or putative ion transport properties. BLAST analysis revealed that a prokaryotic gene (ydfJ) expressed in Escherichia coli K12 strain shared 8.6% homology with Kir6.1 and 8.3% with Kir6.2 genes. Subsequently, we cloned and sequenced ydfJ gene from E. coli K12 and heterologously expressed it in mammalian HEK-293 cells. The whole-cell patch-clamp technique was used to record ion channel currents generated by ydfJ-encoded protein. Heterologous expression of ydfJ gene in HEK-293 cells yielded a novel K(+) channel current that was inwardly rectified and had a reversal potential close to K(+) equilibrium potential. The expressed ydfJ channel was blocked reversibly by low concentration of barium in a dose-dependent fashion. Specific K(ATP) channel openers or blockers did not alter the K(+) current generated by ydfJ expression alone or ydfJ coexpressed with rvSUR1 or rvSUR2B subunits of K(ATP) channel complex. Furthermore, this coexpressed ydfJ/rvSUR1 channels were not inhibited by ATP dialysis. On the other hand, ydfJ K(+) currents were inhibited by protopine (a nonspecific K(+) channel blocker) but not by dofetilide (a HERG channel blocker). In summary, heterologously expressed prokaryotic ydfJ gene formed a novel functional K(+) channel in mammalian cells.
authors: Department of Physiology and Pathophysiology, Fudan University, Shanghai, People's Republic of China.
authors: Guanghua
authors: G
authors: Tang
authors: Bo
authors: B
authors: Jiang
authors: Yuan
authors: Y
authors: Huang
authors: Ming
authors: M
authors: Fu
authors: Lingyun
authors: L
authors: Wu
authors: Rui
authors: R
authors: Wang
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D048168:Escherichia coli K12 / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D017136:Ion Transport; D054086:KATP Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D014162:Transfection; D000099161:Kcnj11 Channel
chemical_list: D000255:Adenosine Triphosphate; D001426:Bacterial Proteins; D054086:KATP Channels; D011188:Potassium; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D000099161:Kcnj11 Channel; C092520:uK-ATP-1 potassium channel