Primary structure, developmental expression and functional properties of an inward rectifier K+ channel of the tunicate

Yoshimichi Murata, H. Okado, Y. Katsuyama, Y. Okamura, Y. Kubo

    Research output: Contribution to journalArticlepeer-review

    7 Citations (Scopus)

    Abstract

    A cDNA encoding for a tunicate inward rectifier K+ channel (TuIRK) was isolated. TuIRK exhibited the highest similarity (approximately 50%) with mammalian Kir2 (IRK) subfamily. Maternal RNA of TuIRK was detected by RT-PCR in unfertilized eggs. By in situ hybridization, the transcript was observed at the 32-cell stage, restricted at the 64-cell stage in anterior epidermal cells of a4-2 blastomere lineage, and disappeared at the late gastrula stage. Therefore, TuIRK was identified to be the inward rectifier whose expression was previously reported to change dramatically upon the neural/epidermal cell fate selection. In Xenopus oocytes, TuIRK expressed a strongly inward rectifying K+ current. The basic electrophysiological properties of TuIRK were similar to those of the mouse IRK1 (mIRK1), except that the sensitivity to the block by extracellular Mg2+ was much lower than that of mIRK1. To identify the structural determinant, we made mutants of the pore region, and then of the extracellular loop (N226 of TuIRK, and E125 of mIRK1). In E125N mutant of mIRK1, the sensitivity to the Mg2+ block was decreased significantly, whereas N226E of TuIRK1 did not acquire the sensitivity. These results demonstrate the contribution of this site to the Mg2+ block and the presence of additional determinant(s).

    Original languageEnglish
    Pages (from-to)387-399
    Number of pages13
    JournalReceptors and Channels
    Volume7
    Issue number5
    Publication statusPublished - 2001 Oct 25

    Keywords

    • cDNA
    • Development
    • Inward rectifier potassium channel
    • Mg block
    • Mutagenesis
    • Tunicate

    ASJC Scopus subject areas

    • Clinical Biochemistry
    • Endocrinology
    • Cell Biology

    Fingerprint

    Dive into the research topics of 'Primary structure, developmental expression and functional properties of an inward rectifier K+ channel of the tunicate'. Together they form a unique fingerprint.

    Cite this