title: Engineering synthetic antibody binders for allosteric inhibition of prolactin receptor signaling.
abstract: BACKGROUND
  Many receptors function by binding to multiple ligands, each eliciting a distinct biological output. The extracellular domain of the human prolactin receptor (hPRL-R) uses an identical epitope to bind to both prolactin (hPRL) and growth hormone (hGH), yet little is known about how each hormone binding event triggers the appropriate response.
  
  
  RESULTS
  Here, we utilized a phage display library to generate synthetic antibodies (sABs) that preferentially modulate hPRL-R function in a hormone-dependent fashion. We determined the crystal structure of a sAB-hPRL-R complex, which revealed a novel allosteric mechanism of antagonism, whereby the sAB traps the receptor in a conformation more suitable for hGH binding than hPRL. This was validated by examining the effect of the sABs on hormone internalization via the hPRL-R and its downstream signaling pathway.
  
  
  CONCLUSIONS
  The findings suggest that subtle structural changes in the extracellular domain of hPRL-R induced by each hormone determine the biological output triggered by hormone binding. We conclude that sABs generated by phage display selection can detect these subtle structural differences, and therefore can be used to dissect the structural basis of receptor-ligand specificity.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA. srizk@nd.edu.|Current Address: Boler -Parseghian Center for Rare and Neglected Diseases, University of Notre Dame, Notre Dame, IN, USA. srizk@nd.edu.
authors.forename: Shahir S
authors.initials: SS
authors.lastname: Rizk
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA. jean-louis.k.kouadio@monsanto.com.|Current Address: Monsanto Co. 700 Chesterfield Parkway, Chesterfield, MO, USA. jean-louis.k.kouadio@monsanto.com.
authors.forename: Jean-Louis K
authors.initials: JL
authors.lastname: Kouadio
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA. a.szymborska@yahoo.com.|Current Address: Max Delbrueck Center for Molecular Medicine, Berlin, Germany. a.szymborska@yahoo.com.
authors.forename: Anna
authors.initials: A
authors.lastname: Szymborska
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA. erica1@gmail.com.
authors.forename: Erica M
authors.initials: EM
authors.lastname: Duguid
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA. somnath.mukherjee80@gmail.com.
authors.forename: Somnath
authors.initials: S
authors.lastname: Mukherjee
authors.affiliation: Department of Pathology, Northwestern University, Chicago, IL, USA. jiamaoz@yahoo.com.
authors.forename: Jiamao
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Pathology, Northwestern University, Chicago, IL, USA. clevenger@northwestern.edu.|Current Address: Department of Pathology, Virginia Commonwealth University, Richmond, VA, USA. clevenger@northwestern.edu.
authors.forename: Charles V
authors.initials: CV
authors.lastname: Clevenger
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA. koss@bsd.uchicago.edu.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Kossiakoff
mesh_terms: D000939:Epitopes / Q000737:chemistry / Q000235:genetics; D019382:Human Growth Hormone / Q000737:chemistry / Q000235:genetics; D006801:Humans; D011388:Prolactin / Q000737:chemistry / Q000235:genetics; D017434:Protein Structure, Tertiary; D011981:Receptors, Prolactin / Q000737:chemistry / Q000235:genetics; D015398:Signal Transduction; D057127:Single-Chain Antibodies / Q000737:chemistry / Q000235:genetics
chemical_list: D000939:Epitopes; D011981:Receptors, Prolactin; D057127:Single-Chain Antibodies; D019382:Human Growth Hormone; D011388:Prolactin