Rationally designed integrin beta3 mutants stabilized in the high affinity conformation.
Integrins are important cell surface receptors that transmit bidirectional signals across the membrane. It has been shown that a conformational change of the integrin beta-subunit headpiece (i.e. the beta I domain and the hybrid domain) plays a critical role in regulating integrin ligand binding affinity and function. Previous studies have used coarse methods (a glycan wedge, mutations in transmembrane contacts) to force the beta-subunit into either the open or closed conformation. Here, we demonstrate a detailed understanding of this conformational change by applying computational design techniques to select five amino acid side chains that play an important role in the energetic balance between the open and closed conformations of alphaIIbbeta3. Eight single-point mutants were designed at these sites, of which five bound ligands much better than wild type. Further, these mutants were found to be in a more extended conformation than wild type, suggesting that the conformational change at the ligand binding headpiece was propagated to the legs of the integrin. This detailed understanding of the conformational change will assist in the development of allosteric drugs that either stabilize or destabilize specific integrin conformations without occluding the ligand-binding site.
Luo
Bing-Hao
BH
Immune Disease Institute and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Karanicolas
John
J
Harmacek
Laura D
LD
Baker
David
D
Springer
Timothy A
TA
D001665:Binding Sites / Q000235:genetics; D003198:Computer Simulation; D006801:Humans; D039661:Integrin beta3 / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics*
D039661:Integrin beta3; D008024:Ligands; D019039:Platelet Glycoprotein GPIIb-IIIa Complex