Assembly of ROMK1 (Kir 1.1a) inward rectifier K+ channel subunits involves multiple interaction sites

Joseph C. Koster, Kristin A. Bentle, Colin G. Nichols, Kevin Ho

Research output: Contribution to journalArticle

29 Scopus citations

Abstract

The ROMK1 (Kir 1.1a) channel is formed by a tetrameric complex of subunits, each characterized by cytoplasmic N- and C-termini and a core region of two transmembrane helices flanking a pore-forming segment. To delineate the general regions mediating the assembly of ROMK1 subunits we constructed epitope-tagged N-terminal C-terminal, and transmembrane segment deletion mutants. Nonfunctional subunits with N-terminal, core region, and C- terminal deletions had dominant negative effects when coexpressed with wild- type ROMK1 subunits in Xenopus oocytes. In contrast, coexpression of these nonfunctional subunits with Kv 2.1 (DRK1) did not suppress Kv 2.1 currents in control oocytes. Interactions between epitope-tagged mutant and wild-type ROMK1 subunits were studied in parallel by immunoprecipitating [35S]- labeled oocyte membrane proteins. Complexes containing both wild-type and mutant subunits that retained H5, M2, and C-terminal regions were coimmunoprecipitated to a greater extent than complexes consisting of wild- type and mutant subunits with core region and/or C-terminal deletions. The present findings are consistent with the hypothesis that multiple interaction sites located in the core region and cytoplasmic termini of ROMK1 subunits mediate homomultimeric assembly.

Original languageEnglish
Pages (from-to)1821-1829
Number of pages9
JournalBiophysical Journal
Volume74
Issue number4
DOIs
StatePublished - Jan 1 1998

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