A small region in phosducin inhibits G-protein betagamma-subunit function.
G-protein betagamma-subunits (G(betagamma)) are active transmembrane signalling components. Their function recently has been observed to be regulated by the cytosolic protein phosducin. We show here that a small fragment (amino acids 215-232) contained in the C-terminus of phosducin is sufficient for high-affinity interactions with G(betagamma). Corresponding peptides not only disrupt G(betagamma)-G(alpha) interactions, as defined by G(betagamma)-stimulated GTPase activity of alpha(o), but also other G(betagamma)-mediated functions. The NMR structure of a peptide encompassing this region shows a loop exposing the side chains of Glu223 and Tyr224, and peptides with a substitution of either of these amino acids show a complete loss of activity towards G(o). Mutation of this Tyr224 to Ala in full-length phosducin reduced the functional activity of phosducin to that of phosducin's isolated N-terminus, indicating the importance of this residue within the short, structurally defined C-terminal segment. This small peptide derived from phosducin, may represent a model of a G(betagamma) inhibitor, and illustrates the potential of small compounds to affect G(betagamma) functions.
Blüml
K
K
Institut für Pharmakologie und Toxikologie der Universität Würzburg, Germany.
Schnepp
W
W
Schröder
S
S
Beyermann
M
M
Macias
M
M
Oschkinat
H
H
Lohse
M J
MJ
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D018360:Crystallography, X-Ray; D005136:Eye Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020555:GTP-Binding Protein Regulators; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology
D005136:Eye Proteins; D020555:GTP-Binding Protein Regulators; D010446:Peptide Fragments; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C065631:phosducin; D011494:Protein Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins