The α4ß1/EMILIN1 interaction discloses a novel and unique integrin-ligand type of engagement.
Matrix Biol
; 66: 50-66, 2018 03.
Article
en En
| MEDLINE
| ID: mdl-29037761
EMILIN1, a homo-trimeric adhesive ECM glycoprotein, interacts with the α4ß1 integrin through its gC1q domain. Uniquely among the C1q family members, the EMILIN1 gC1q presents only nine-stranded ß-sandwich fold and the missing strand is substituted by a disordered 19-residue long segment spanning from Y927 to G945 at the apex of the gC1q domain. This unstructured loop exposes to the solvent the acidic residue E933, which plays a key role in the α4ß1 integrin mediated interaction. Here, we experimentally determined that the three E933 residues (one from each monomer) are all required for ligand binding. By docking the NMR structure of the gC1q to a virtual α4ß1 crystal structure based on the known structures of α4ß7 and α5ß1 integrins we built a model of α4ß1-gC1q complex where three E933 residues are smoothly forced to coordinate the Mg2+ ion at the ßI MIDAS site of the integrin. By bringing the three E933 close in space, the trimeric supramolecular organization of gC1q allows the formation of a proper 3D geometry and suggests a quaternary-structure-dependent mode of interaction. Furthermore, we experimentally identified R904 as a synergistic residue for cell adhesion. Accordingly, the model showed that this residue is able to form potential stabilizing intra-chain salt bridges with residues E928 and E930. This mode of interaction likely accounts for a more stable and durable α4ß1-gC1q interaction in comparison with the prototypic CS1 ligand. To our knowledge, this is the first report describing the simultaneous involvement of all the three acidic residues of a trimeric ligand in the formation of a dimeric complex with the integrin ßI domain.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Glicoproteínas de Membrana
/
Integrina alfa4beta1
Límite:
Humans
Idioma:
En
Revista:
Matrix Biol
Asunto de la revista:
BIOLOGIA MOLECULAR
/
BIOQUIMICA
Año:
2018
Tipo del documento:
Article
País de afiliación:
Italia
Pais de publicación:
Países Bajos