Position of Pro and Ser near Glu7.32 in the extracellular loop 3 of mammalian and nonmammalian gonadotropin-releasing hormone (GnRH) receptors is a critical determinant for differential ligand selectivity for mammalian GnRH and chicken GnRH-II.
A Glu/Asp7.32 residue in the extracellular loop 3 of the mammalian GnRH receptor (GnRHR) is known to interact with Arg8 of mammalian GnRH (mGnRH), which may confer preferential ligand selectivity for mGnRH than for chicken GnRH-II (cGnRH-II). However, some nonmammalian GnRHRs also have the Glu/Asp residue at the same position, yet respond better to cGnRH-II than mGnRH. Amino acids flanking Glu/Asp7.32 are differentially arranged such that mammalian and nonmammalian GnRHRs have an S-E/D-P motif and P-X-S/Y motif, respectively. We presumed the position of Ser7.31 or Pro7.33 of rat GnRHR as a potential determinant for ligand selectivity. Either placing Pro before Glu7.32 or placing Ser after Glu7.32 significantly decreased the sensitivity and/or efficacy for mGnRH, but slightly increased that for cGnRH-II in several mutant receptors. Among them, those with a PEV, PES, or SES motif exhibited a marked decrease in sensitivity for mGnRH such that cGnRH-II had a higher potency than mGnRH, showing a reversed preferential ligand selectivity. Chimeric mGnRHs in which positions 5, 7, and/or 8 were replaced by those of cGnRH-II revealed a greater ability to activate these mutant receptors than mGnRH, whereas they were less potent to activate wild-type rat GnRHR than mGnRH. Interestingly, a mutant bullfrog type I receptor with the SEP motif exhibited an increased sensitivity for mGnRH but a decreased sensitivity for cGnRH-II. These results indicate that the position of Pro and Ser near Glu7.32 in the extracellular loop 3 is critical for the differential ligand selectivity between mammalian and nonmammalian GnRHRs.
Wang
Chengbing
C
Hormone Research Center, Chonnam National University, Gwangju 500-757, Republic of Korea.
Yun
Oim
O
Maiti
Kaushik
K
Oh
Da Young
DY
Oh
Da Young
da Y
Kim
Kyeong Kyu
KK
Chae
Chong Hak
CH
Lee
Chang Jun
CJ
Seong
Jae Young
JY
Kwon
Hyuk Bang
HB
D000818:Animals; D002645:Chickens; D017931:DNA Primers; D018698:Glutamic Acid; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D008322:Mammals; D008958:Models, Molecular; D008968:Molecular Conformation; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D011392:Proline; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D051381:Rats; D011966:Receptors, LHRH / Q000737:chemistry* / Q000378:metabolism*; D012694:Serine; D013045:Species Specificity; D013379:Substrate Specificity
D017931:DNA Primers; D008024:Ligands; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D018698:Glutamic Acid; D012694:Serine; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-; D011392:Proline