Crystal structure of an affinity-matured prolactin complexed to its dimerized receptor reveals the topology of hormone binding site 2.
We report the first crystal structure of a 1:2 hormone.receptor complex that involves prolactin (PRL) as the ligand, at 3.8-A resolution. Stable ternary complexes were obtained by generating affinity-matured PRL variants harboring an N-terminal tail from ovine placental lactogen, a closely related PRL receptor (PRLR) ligand. This structure allows one to draw up an exhaustive inventory of the residues involved at the PRL.PRLR site 2 interface, consistent with all previously reported site-directed mutagenesis data. We propose, with this description, an interaction model involving three structural components of PRL site 2 ("three-pin plug"): the conserved glycine 129 of helix alpha3, the hydrogen bond network involving surrounding residues (glycine cavity), and the N terminus. The model provides a molecular basis for the properties of the different PRL analogs designed to date, including PRLR antagonists. Finally, comparison of our 1:2 PRL.PRLR(2) structure with those of free PRL and its 1:1 complex indicates that the structure of PRL undergoes significant changes when binding the first, but not the second receptor. This suggests that the second PRLR moiety adapts to the 1:1 complex rather than the opposite. In conclusion, this structure will be a useful guiding tool for further investigations of the molecular mechanisms involved in PRLR dimerization and activation, as well as for the optimization of PRLR antagonists, an emerging class of compounds with high therapeutic potential against breast and prostate cancer.
Broutin
Isabelle
I
Laboratoire de Cristallographie et RMN Biologiques, CNRS, UMR 8015, Université Paris Descartes, 75006 Paris, France.
Jomain
Jean-Baptiste
JB
Tallet
Estelle
E
van Agthoven
Jan
J
Raynal
Bertrand
B
Hoos
Sylviane
S
Kragelund
Birthe B
BB
Kelly
Paul A
PA
Ducruix
Arnaud
A
England
Patrick
P
Goffin
Vincent
V
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003461:Crystallography; D019281:Dimerization; D015195:Drug Design; D005998:Glycine / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010928:Placental Lactogen / Q000737:chemistry / Q000235:genetics; D011388:Prolactin / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D011981:Receptors, Prolactin / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D012756:Sheep; D013329:Structure-Activity Relationship; D020349:Surface Plasmon Resonance; D014961:X-Ray Diffraction
D011981:Receptors, Prolactin; D011994:Recombinant Proteins; D011388:Prolactin; D010928:Placental Lactogen; D005998:Glycine