Rhodopsin-transducin coupling: role of the Galpha C-terminus in nucleotide exchange catalysis.
In the early steps of visual signal transduction, light-activated rhodopsin (R*) catalyzes GDP/GTP exchange in the heterotrimeric G protein (Galphabetagamma) transducin. We recently reported that the catalytic interaction involves two sequential steps. An initial docking between R* and Gbetagamma leads to conformational changes which make the C-terminus of Galpha (CTalpha) available for binding to R*. Binding of CTalpha by R* then triggers GDP/GTP exchange in the Galpha subunit. To further study this two-step mechanism, we investigated different single amino acid substitutions within CTalpha and discuss the effects of high affinity mutations on nucleotide exchange catalysis.
Herrmann
Rolf
R
Institut für medizinische Physik und Biophysik (CCM), Charité-Universitätsmedizin Berlin, Schumannstr. 20/21, 10098 Berlin, Germany. rolf.herrmann@duke.edu
Heck
Martin
M
Henklein
Peter
P
Kleuss
Christiane
C
Wray
Victor
V
Hofmann
Klaus Peter
KP
Ernst
Oliver P
OP
D019943:Amino Acid Substitution; D000818:Animals; D002417:Cattle; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D011485:Protein Binding; D011487:Protein Conformation; D012243:Rhodopsin / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D020079:Terminal Repeat Sequences; D015293:Transducin / Q000378:metabolism*; D014785:Vision, Ocular / Q000502:physiology
D044385:GTP-Binding Protein alpha Subunits; D012243:Rhodopsin; D015293:Transducin