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Type: Journal article
Title: Block by extracellular divalent cations of Drosophila big brain channels expressed in Xenopus oocytes
Author: Yanochko, G.
Yool, A.
Citation: Biophysical Journal, 2004; 86(3):1470-1478
Publisher: Biophysical Society
Issue Date: 2004
ISSN: 0006-3495
Statement of
Gina M. Yanochko and Andrea J. Yool
Abstract: Drosophila Big Brain (BIB) is a transmembrane protein encoded by the neurogenic gene big brain (bib), which is important for early development of the fly nervous system. BIB expressed in Xenopus oocytes is a monovalent cation channel modulated by tyrosine kinase signaling. Results here demonstrate that the BIB conductance shows voltage- and dose-dependent block by extracellular divalent cations Ca2+ and Ba2+ but not by Mg2+ in wild-type channels. Site-directed mutagenesis of negatively charged glutamate (Glu274) and aspartate (Asp253) residues had no effect on divalent cation block. However, mutation of a conserved glutamate at position 71 (Glu71) in the first transmembrane domain (M1) altered channel properties. Mutation of Glu71 to Asp introduced a new sensitivity to block by extracellular Mg2+; substitutions with asparagine or glutamine decreased whole-cell conductance; and substitution with lysine compromised plasma membrane expression. Block by divalent cations is important in other ion channels for voltage-dependent function, enhanced signal resolution, and feedback regulation. Our data show that the wild-type BIB conductance is attenuated by external Ca2+, suggesting that endogenous divalent cation block might be relevant for enhancing signal resolution or voltage dependence for the native signaling process in neuronal cell fate determination.
Keywords: Oocytes
Cells, Cultured
Extracellular Fluid
Xenopus laevis
Cations, Divalent
Ion Channels
Drosophila Proteins
Membrane Proteins
Recombinant Proteins
Mutagenesis, Site-Directed
Ion Channel Gating
Structure-Activity Relationship
Membrane Potentials
Description: Copyright © 2004 The Biophysical Society
DOI: 10.1016/S0006-3495(04)74215-0
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Appears in Collections:Aurora harvest
Molecular and Biomedical Science publications

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