Inhibition of G-protein betagamma-subunit functions by phosducin-like protein.
Phosducin is a cytosolic protein predominantly expressed in the retina and the pineal gland that can interact with the betagamma subunits of guanine nucleotide binding proteins (G proteins) and thereby may regulate transmembrane signaling. A cDNA encoding a phosducin-like protein (PhLP) has recently been isolated from rat brain [Miles, M. F., Barhite, S., Sganga, M. & Elliott, M. (1993) Proc. Natl. Acad. Sci. USA 90, 10831-10835. Here we report the expression of PhLP in Escherichia coli and its purification. Recombinant purified PUP inhibited multiple effects of G-protein betagamma subunits. First, it inhibited the betagamma-subunit-dependent ADP-ribosylation of purified alpha(o) by pertussis toxin. Second, it inhibited the GTPase activity of purified G(o). The IC50 value of PhLP in the latter assay was 89 nM, whereas phosducin caused half-maximal inhibition at 17 nM. And finally, PhLP antagonized the enhancement of rhodopsin phosphorylation by purified betagamma subunits. The N terminus of PhLP shows no similarity to the much longer N terminus of phosducin, the region shown to be critical for phosducin-betagamma-subunit interactions. Therefore, PhLP appears to bind to G-protein betagamma subunits by an as yet unknown mode of interaction and may represent an endogenous regulator of G-protein function.
Schröder
S
S
Laboratory of Molecular Biology, University of Munich, Germany.
Lohse
M J
MJ
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D004791:Enzyme Inhibitors; D005136:Eye Proteins / Q000737:chemistry*; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors; D020555:GTP-Binding Protein Regulators; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors*; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000302:isolation & purification / Q000378:metabolism*; D037342:Pertussis Toxin; D010750:Phosphoproteins / Q000737:chemistry*; D010766:Phosphorylation; D051381:Rats; D011994:Recombinant Proteins; D012243:Rhodopsin / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D010566:Virulence Factors, Bordetella / Q000037:antagonists & inhibitors
D002352:Carrier Proteins; D017931:DNA Primers; D004791:Enzyme Inhibitors; D005136:Eye Proteins; D020555:GTP-Binding Protein Regulators; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; C498320:Pdcl protein, rat; D010750:Phosphoproteins; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; C065631:phosducin; D012243:Rhodopsin; D037342:Pertussis Toxin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins