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J. Cell Biol. 171 (3): 517-526

Copyright © 2005 by the Rockefeller University Press.


Excess of Gße over Gq{alpha}e in vivo prevents dark, spontaneous activity of Drosophila photoreceptors

Natalie Elia1, Shahar Frechter2, Yinon Gedi1, Baruch Minke2, , and Zvi Selinger1

1 Department of Biological Chemistry, Kühne Minerva Center for Studies of Visual Transduction, Institute of Life Sciences, The Hebrew University, Givat Ram, Jerusalem 91904, Israel
2 Department of Physiology, Kühne Minerva Center for Studies of Visual Transduction, Institute of Life Sciences, The Hebrew University, Givat Ram, Jerusalem 91904, Israel

Correspondence to Zvi Selinger: selinger{at}

Abstract: Drosophila melanogaster photoreceptor cells are capable of detecting single photons. This utmost sensitivity is critically dependent on the maintenance of an exceedingly low, dark, spontaneous activity of photoreceptor cells. However, the underlying mechanisms of this hallmark of phototransduction are not fully understood. An analysis of the Drosophila visual heterotrimeric ({alpha}ß{gamma}) Gq protein revealed that wild-type Drosophila flies have about a twofold excess of Gß over G{alpha} subunits of the visual Gq protein. Studies of Gße mutants in which the excess of Gß was genetically eliminated showed dramatic dark, spontaneous activity of the photoreceptor cells, whereas concurrent genetic reduction of the G{alpha} subunit, which restored the excess of Gß, abolished this effect. These results indicate that an excess of Gß over G{alpha} is a strategy used in vivo for the suppression of spontaneous activity, thereby yielding a high signal to noise ratio, which is characteristic of the photoreceptor light response. This mechanism could be relevant to the regulation of G protein signaling in general.

N. Elia and S. Frechter contributed equally to this paper.

Abbreviations used in this paper: ERG, electroretinogram; GDP, guanosine diphosphate.

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