Structures of adnectin/protein complexes reveal an expanded binding footprint.
Adnectins are targeted biologics derived from the tenth type III domain of human fibronectin (¹⁰Fn3), a member of the immunoglobulin superfamily. Target-specific binders are selected from libraries generated by diversifying the three ¹⁰Fn3 loops that are analogous to the complementarity determining regions of antibodies. The crystal structures of two Adnectins were determined, each in complex with its therapeutic target, EGFR or IL-23. Both Adnectins bind different epitopes than those bound by known monoclonal antibodies. Molecular modeling suggests that some of these epitopes might not be accessible to antibodies because of the size and concave shape of the antibody combining site. In addition to interactions from the Adnectin diversified loops, residues from the N terminus and/or the β strands interact with the target proteins in both complexes. Alanine-scanning mutagenesis confirmed the calculated binding energies of these β strand interactions, indicating that these nonloop residues can expand the available binding footprint.
Bristol-Myers Squibb Research & Development, Princeton, NJ 08543-4000, USA.
Vidhyashankar
V
Ramamurthy
Stanley R
SR
Krystek
Alexander
A
Bush
Anzhi
A
Wei
Stuart L
SL
Emanuel
Ruchira
R
Das Gupta
Ahsen
A
Janjua
Lin
L
Cheng
Melissa
M
Murdock
Bozena
B
Abramczyk
Daniel
D
Cohen
Zheng
Z
Lin
Paul
P
Morin
Jonathan H
JH
Davis
Michael
M
Dabritz
Douglas C
DC
McLaughlin
Katie A
KA
Russo
Ginger
G
Chao
Martin C
MC
Wright
Victoria A
VA
Jenny
Linda J
LJ
Engle
Eric
E
Furfine
Steven
S
Sheriff
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D018360:Crystallography, X-Ray; D066246:ErbB Receptors / Q000737:chemistry*; D005353:Fibronectins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D006860:Hydrogen Bonding; D053759:Interleukin-23 / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D040681:Structural Homology, Protein; D020349:Surface Plasmon Resonance; D013499:Surface Properties
D005353:Fibronectins; D053759:Interleukin-23; D046912:Multiprotein Complexes; D010446:Peptide Fragments; D066246:ErbB Receptors