Tracing the origin of the RACTK1 K+ channel

Potassium secretion by the kidney is vital for the maintenance of K+ homeos tasis. RACTK1, a putative inwardly rectifying potassium channel cloned from cultured rabbit collecting duct cells, has been proposed to play a role in this process. However, the lack of homology with any other cloned potassiu m channel and the inability to reproduce the results across different labor atories has brought into question the existence of RACTK1. Recently, it has been suggested that RACTK1 is a contamination from Escherichia coli. In th is work we add conclusive evidence supporting the bacterial origin of RACTK 1. Using both genomic PCR and RT-PCR we were unable to detect RACTK1 in a n umber of mammalian species. In addition sequencing of RACTK1 cDNA confirmed a complete homology between RACTK1 and a region of E. coli genomic DNA. Fi nally, a hypothesis on how RACTK1 could have been generated from a contamin ation by E. coli genomic DNA is presented. (C) 2000 Academic Press.