Noncompetitive antibody neutralization of IL-10 revealed by protein engineering and x-ray crystallography.
IL-10 is a dimeric cytokine that must engage its high-affinity cell surface receptor, IL-10R1, to induce multiple cellular activities. Here we report the 1.9 A crystal structure of an engineered IL-10 monomer (IL-10M1) in complex with a neutralizing Fab fragment (9D7Fab). 9D7Fab and IL-10R1 bind distinct nonoverlapping surfaces on IL-10M1. Antagonism of the IL-10M1/IL-10R1 interaction is the result of 9D7Fab-induced conformational changes in the CD loop of IL-10M1 that indirectly alter the structure of the IL-10R1 binding site. A single mutation (Ile87Ala) in the same CD loop region of the Epstein-Barr virus IL-10 (ebvIL-10) also reduces IL-10R1 binding affinity, suggesting that ebvIL-10 and 9D7Fab use similar allosteric mechanisms to modulate IL-10R1 affinity and biological activity.
Center for Biophysical Sciences and Engineering, University of Alabama, Birmingham, 35294, USA.
Kristopher
K
Josephson
Brandi C
BC
Jones
Leigh J
LJ
Walter
Ruth
R
DiGiacomo
Stephen R
SR
Indelicato
Mark R
MR
Walter
D000494:Allosteric Regulation; D018360:Crystallography, X-Ray; D004854:Herpesvirus 4, Human / Q000737:chemistry; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry*; D016753:Interleukin-10 / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D015202:Protein Engineering; D018123:Receptors, Interleukin / Q000737:chemistry; D053701:Receptors, Interleukin-10
D007140:Immunoglobulin Fab Fragments; D018123:Receptors, Interleukin; D053701:Receptors, Interleukin-10; D016753:Interleukin-10