Structural predictions for the ligand-binding region of glycoprotein hormone receptors and the nature of hormone-receptor interactions.
BACKGROUND
Glycoprotein hormones influence the development and function of the ovary, testis and thyroid by binding to specific high-affinity receptors. The extracellular domains of these receptors are members of the leucine-rich repeat (LRR) protein superfamily and are responsible for the high-affinity binding. The crystal structure of a glycoprotein hormone, namely human choriogonadotropin (hCG), is known, but neither the receptor structure, mode of hormone binding, nor mechanism for activation, have been established.


RESULTS
Despite very low sequence similarity between exon-demarcated LRRs in the receptors and the LRRs of porcine ribonuclease inhibitor (RI), the secondary structures for the two repeat sets are found to be alike Constraints on curvature and beta-barrel geometry from the sequence pattern for repeated beta alpha units suggest that the receptors contain three-dimensional structures similar to that of RI. With the RI crystal structure as a template, models were constructed for exons 2-8 of the receptors. The model for this portion of the choriogonadotropin receptor is complementary in shape and electrostatic characteristics to the surface of hCG at an identified focus of hormone-receptor interaction.


CONCLUSIONS
The predicted models for the structures and mode of hormone binding of the glycoprotein hormone receptors are to a large extent consistent with currently available biochemical and mutational data. Repeated sequences in beta-barrel proteins are shown to have general implications for constraints on structure. Averaging techniques used here to recognize the structural motif in these receptors should also apply to other proteins with repeated sequences.
Jiang
X
X
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
Dreano
M
M
Buckler
D R
DR
Cheng
S
S
Ythier
A
A
Wu
H
H
Hendrickson
W A
WA
el Tayar
N
N
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006063:Chorionic Gonadotropin / Q000378:metabolism; D003553:Cystine / Q000737:chemistry; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006031:Glycosylation; D006728:Hormones / Q000378:metabolism*; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011485:Protein Binding; D017433:Protein Structure, Secondary; D051381:Rats; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000378:metabolism; D011962:Receptors, FSH / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011974:Receptors, LH / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011989:Receptors, Thyrotropin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D013552:Swine; D013972:Thyrotropin / Q000378:metabolism
D006063:Chorionic Gonadotropin; D006728:Hormones; D011956:Receptors, Cell Surface; D011962:Receptors, FSH; D011974:Receptors, LH; D011989:Receptors, Thyrotropin; D003553:Cystine; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D019204:GTP-Binding Proteins