Molecular Aspects of Signal Transduction in the Visual System 
processes photoreceptor signals. The DGOa pro- 
tein is a substrate for pertussis toxin, an ADP-ribo- 
syl transferase that inactivates GOa subunits. We 
produced transgenic Drosophila that express a 
heat-shock-inducible pertussis toxin gene in 
most tissues of the fly, including the lamina. Per- 
tussis toxin expression in these flies alters a 
transient component of the electroretinograms 
normally generated in the lamina. The photore- 
ceptor component of the electroretinograms is 
normal, suggesting that pertussis toxin has un- 
coupled a normal photoreceptor response from 
its perception in the brain. 
The long-term objective addressed in these 
projects is to identify the biochemical mecha- 
nisms by which cells determine their responses 
to stimuli in order to perform specific physiologi- 
cal functions. 
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