Abstract
Phosducin is a 33-kDa cytosolic regulator of G-protein-mediated signaling
that has previously been thought to be specific for retina and pineal
gland. In this study, we show widespread tissue distribution of phosducin
by the amplification of its cDNA and the detection of two different
transcripts in Northern analyses in liver, lung, heart, brain, and
retina. On the protein level, phosducin could be detected in 12 bovine
tissues by immune precipitation and subsequent Western analysis using
anti-phosducin antibodies generated in two different species. Masking
of phosducin in direct Western blots appears to explain the failure
to detect phosducin in earlier studies. The concentration of phosducin
in bovine brain was calculated in the range of 10 pmol/mg total cytosolic
protein (approximately 1 microM), whereas in the other tissues, it
was slightly less. In these concentrations, phosducin inhibited receptor-stimulated
adenylyl cyclase activity in cell membranes by about 50%. Taken together,
our results indicate that phosducin is a ubiquitous regulator of
G-protein function.
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