PMID: 24692540

Authors:

Mahalingam B, Van Agthoven JF, Xiong JP, Alonso JL, Adair BD, Rui X, Anand S, Mehrbod M, Mofrad MR, Burger C, Goodman SL, Arnaout MA

Title:

Atomic basis for the species-specific inhibition of alphaV integrins by monoclonal antibody 17E6 is revealed by the crystal structure of alphaVbeta3 ectodomain-17E6 Fab complex.

Journal:

J Biol Chem. 2014 May 16;289(20):13801-9. doi: 10.1074/jbc.M113.546929. Epub 2014, Apr 1.

Abstract:

The function-blocking, non-RGD-containing, and primate-specific mouse monoclonal antibody 17E6 binds the alphaV subfamily of integrins. 17E6 is currently in phase II clinical trials for treating cancer. To elucidate the structural basis of recognition and the molecular mechanism of inhibition, we crystallized alphaVbeta3 ectodomain in complex with the Fab fragment of 17E6. Protein crystals grew in presence of the activating cation Mn(2+). The integrin in the complex and in solution assumed the genuflected conformation. 17E6 Fab bound exclusively to the Propeller domain of the alphaV subunit. At the core of alphaV-Fab interface were interactions involving Propeller residues Lys-203 and Gln-145, with the latter accounting for primate specificity. The Propeller residue Asp-150, which normally coordinates Arg of the ligand Arg-Gly-Asp motif, formed contacts with Arg-54 of the Fab that were expected to reduce soluble FN10 binding to cellular alphaVbeta3 complexed with 17E6. This was confirmed in direct binding studies, suggesting that 17E6 is an allosteric inhibitor of alphaV integrins.