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https://hdl.handle.net/2440/34787
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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 1542-0086 |
Statement of Responsibility: | 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 Animals Xenopus laevis Drosophila Cations, Divalent Barium Calcium Magnesium 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 |
Published version: | http://www.biophysj.org/cgi/content/abstract/86/3/1470 |
Appears in Collections: | Aurora harvest Molecular and Biomedical Science publications |
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