Complete integrin headpiece opening in eight steps

Carefully soaking crystals with Arg-Gly-Asp (RGD) peptides, we captured eight distinct RGD-bound conformations of the αIIbβ3 integrin headpiece. Starting from the closed βI domain conformation, we saw six intermediate βI conformations and finally the fully open βI with the hybrid domain swung out in the crystal lattice. The β1-α1 backbone that hydrogen bonds to the Asp side chain of RGD was the first element to move followed by adjacent to metal ion-dependent adhesion site Ca2+, α1 helix, α1’ helix, β6-α7 loop, α7 helix, and hybrid domain. We define in atomic detail how conformational change was transmitted over long distances in integrins, 40 Å from the ligand binding site to the opposite end of the βI domain and 80 Å to the far end of the hybrid domain. During these movements, RGD slid in its binding groove toward αIIb, and its Arg side chain became ordered. RGD concentration requirements in soaking suggested a >200-fold higher affinity after opening. The thermodynamic cycle shows how higher affinity pays the energetic cost of opening.

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Variation in One Residue Associated with the Metal Ion-Dependent Adhesion Site Regulates αIIbβ3 Integrin Ligand Binding Affinity

PLoS ONE ◽

10.1371/journal.pone.0076793 ◽

2013 ◽

Vol 8 (10) ◽

pp. e76793 ◽

Cited By ~ 3

Author(s):

Joel Raborn ◽

Ting Fu ◽

Xue Wu ◽

Zhilong Xiu ◽

Guohui Li ◽

...

Keyword(s):

Ligand Binding ◽

Binding Affinity ◽

Metal Ion ◽

Integrin Ligand ◽

Αiibβ3 Integrin ◽

Adhesion Site

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Structural specializations of α4β7, an integrin that mediates rolling adhesion

The Journal of Cell Biology ◽

10.1083/jcb.201110023 ◽

2012 ◽

Vol 196 (1) ◽

pp. 131-146 ◽

Cited By ~ 56

Author(s):

Yamei Yu ◽

Jianghai Zhu ◽

Li-Zhi Mi ◽

Thomas Walz ◽

Hao Sun ◽

...

Keyword(s):

Electron Microscopy ◽

Multiple Sclerosis ◽

Ligand Binding ◽

Adhesion Molecule ◽

Metal Ion ◽

Immunoglobulin Superfamily ◽

Lymphocyte Homing ◽

Homing Receptor ◽

Binding Groove ◽

Adhesion Site

The lymphocyte homing receptor integrin α4β7 is unusual for its ability to mediate both rolling and firm adhesion. α4β1 and α4β7 are targeted by therapeutics approved for multiple sclerosis and Crohn’s disease. Here, we show by electron microscopy and crystallography how two therapeutic Fabs, a small molecule (RO0505376), and mucosal adhesion molecule-1 (MAdCAM-1) bind α4β7. A long binding groove at the α4–β7 interface for immunoglobulin superfamily domains differs in shape from integrin pockets that bind Arg-Gly-Asp motifs. RO0505376 mimics an Ile/Leu-Asp motif in α4 ligands, and orients differently from Arg-Gly-Asp mimics. A novel auxiliary residue at the metal ion–dependent adhesion site in α4β7 is essential for binding to MAdCAM-1 in Mg2+ yet swings away when RO0505376 binds. A novel intermediate conformation of the α4β7 headpiece binds MAdCAM-1 and supports rolling adhesion. Lack of induction of the open headpiece conformation by ligand binding enables rolling adhesion to persist until integrin activation is signaled.

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Structures of the human Pals1 PDZ domain with and without ligand suggest gated access of Crb to the PDZ peptide-binding groove

Acta Crystallographica Section D Biological Crystallography ◽

10.1107/s139900471402776x ◽

2015 ◽

Vol 71 (3) ◽

pp. 555-564 ◽

Cited By ~ 13

Author(s):

Marina E. Ivanova ◽

Georgina C. Fletcher ◽

Nicola O'Reilly ◽

Andrew G. Purkiss ◽

Barry J. Thompson ◽

...

Keyword(s):

Binding Affinity ◽

Protein Interaction ◽

Protein Complexes ◽

Transmembrane Protein ◽

Pdz Domain ◽

Peptide Binding ◽

Side Chain ◽

Apical Plasma Membrane ◽

Peptide Binding Groove ◽

Binding Groove

Many components of epithelial polarity protein complexes possess PDZ domains that are required for protein interaction and recruitment to the apical plasma membrane. Apical localization of the Crumbs (Crb) transmembrane protein requires a PDZ-mediated interaction with Pals1 (protein-associated with Lin7, Stardust, MPP5), a member of the p55 family of membrane-associated guanylate kinases (MAGUKs). This study describes the molecular interaction between the Crb carboxy-terminal motif (ERLI), which is required forDrosophilacell polarity, and the Pals1 PDZ domain using crystallography and fluorescence polarization. Only the last four Crb residues contribute to Pals1 PDZ-domain binding affinity, with specificity contributed by conserved charged interactions. Comparison of the Crb-bound Pals1 PDZ structure with an apo Pals1 structure reveals a key Phe side chain that gates access to the PDZ peptide-binding groove. Removal of this side chain enhances the binding affinity by more than fivefold, suggesting that access of Crb to Pals1 may be regulated by intradomain contacts or by protein–protein interaction.

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Tailoring of Integrin Ligands: Probing the Charge Capability of the Metal Ion-Dependent Adhesion Site

Journal of Medicinal Chemistry ◽

10.1021/jm2013826 ◽

2012 ◽

Vol 55 (2) ◽

pp. 871-882 ◽

Cited By ~ 9

Author(s):

Markus Bollinger ◽

Florian Manzenrieder ◽

Roman Kolb ◽

Alexander Bochen ◽

Stefanie Neubauer ◽

...

Keyword(s):

Metal Ion ◽

Integrin Ligands ◽

Adhesion Site

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Five-coordinate iron(II) porphyrins derived from meso-α,β,γ,δ tetraphenylporphin: synthesis, characterization, and coordinating properties

Canadian Journal of Chemistry ◽

10.1139/v79-288 ◽

1979 ◽

Vol 57 (14) ◽

pp. 1804-1813 ◽

Cited By ~ 36

Author(s):

Michel Momenteau ◽

Bernard Loock ◽

Emile Bisagni ◽

Michel Rougee

Keyword(s):

Metal Ion ◽

Side Chain ◽

Intramolecular Coordination ◽

Trans Isomers ◽

Visible Spectroscopy ◽

Cis And Trans Isomers ◽

The Stability ◽

Heterogeneous Reduction ◽

Cis And Trans ◽

Reduced Forms

Meso-α,β,γ,δ, tetraphenylporphin derivatives bearing acrylic (cis and trans isomers) and propionic side chains with a terminal imidazole group have been synthesized. Intermediate compounds obtained during their preparation were characterized by visible spectroscopy and nmr. In non-coordinating solvents (benzene or toluene), the iron(III) complexes of these compounds do not show intramolecular coordination of the terminal base on the metal ion. The reduced forms of the compounds have been obtained from ferric forms by heterogeneous reduction with aqueous dithionite and exhibit optical spectra characteristic of five-coordinate ferrous complexes. The nitrogenous bases and carbon monoxide affinities of the latter have been measured and the results indicate that the 'transinfluence' exerted by the terminal imidazole does not depend greatly on the nature and the structure of the covalent side chain. In contrast the stability of the five-coordinate compounds depends on the side chain (trans acrylic < propionic < cis acrylic) as suggested by the values reported for the replacement constants of the terminal imidazole by 4-cyanopyridine in unsymmetrical six-coordinate derivatives. The stability of these compounds towards oxidation is also reported.

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