TY - JOUR
T1 - Essential role for the second extracellular loop in C5a receptor activation
AU - Klco, Jeffery M.
AU - Wiegand, Christina B.
AU - Narzinski, Kirk
AU - Baranski, Thomas J.
N1 - Funding Information:
We thank G. Nikiforovich, H. Bourne, K. Blumer, E. Meng and members of the Baranski lab for helpful discussions and review of the manuscript. This work was supported by an award from the American Heart Association (J.M.K.) and by grants from the American Cancer Society IRG-58-010-43 (T.J.B.), the Culpeper Award, Rockefeller Brothers Fund (T.J.B.), and the US National Institutes of Health, GM63720-01 (T.J.B.).
PY - 2005
Y1 - 2005
N2 - More than 90% of G protein-coupled receptors (GPCRs) contain a disulfide bridge that tethers the second extracellular loop (EC2) to the third transmembrane helix. To determine the importance of EC2 and its disulfide bridge in receptor activation, we subjected this region of the complement factor 5a receptor (C5aR) to random saturation mutagenesis and screened for functional receptors in yeast. The cysteine forming the disulfide bridge was the only conserved residue in the EC2-mutated receptors. Notably, -80% of the functional receptors exhibited potent constitutive activity. These results demonstrate an unexpected role for EC2 as a negative regulator of C5a receptor activation. We propose that in other GPCRs, EC2 might serve a similar role by stabilizing the inactive state of the receptor.
AB - More than 90% of G protein-coupled receptors (GPCRs) contain a disulfide bridge that tethers the second extracellular loop (EC2) to the third transmembrane helix. To determine the importance of EC2 and its disulfide bridge in receptor activation, we subjected this region of the complement factor 5a receptor (C5aR) to random saturation mutagenesis and screened for functional receptors in yeast. The cysteine forming the disulfide bridge was the only conserved residue in the EC2-mutated receptors. Notably, -80% of the functional receptors exhibited potent constitutive activity. These results demonstrate an unexpected role for EC2 as a negative regulator of C5a receptor activation. We propose that in other GPCRs, EC2 might serve a similar role by stabilizing the inactive state of the receptor.
UR - http://www.scopus.com/inward/record.url?scp=18744402177&partnerID=8YFLogxK
U2 - 10.1038/nsmb913
DO - 10.1038/nsmb913
M3 - Article
C2 - 15768031
AN - SCOPUS:18744402177
SN - 1545-9993
VL - 12
SP - 320
EP - 326
JO - Nature Structural and Molecular Biology
JF - Nature Structural and Molecular Biology
IS - 4
ER -