Rhodostomin and Trimucrin differentially recognize integrin αvβ3, stabilizing an extended-open conformation via distinct sites

The integrin αvβ3 receptor plays a critical role in various pathological processes, including angiogenesis, tumor growth, and inflammation. While short RGD (arginine-glycine-aspartic acid) peptides can inhibit integrins, their efficacy is often limited. Disintegrins like Rhodostomin (Rho) and Trimucrin (Tmu), which also contain the RGD motif, exhibit superior integrin inhibition. However, the precise structural mechanisms underlying their differential recognition of integrin αvβ3 and their enhanced inhibitory action compared to simpler RGD peptides remained largely uncharacterized, hindering the rational design of more potent and selective integrin-targeted therapeutics.

This study determined the X-ray structure of Trimucrin and utilized cryo-electron microscopy (cryo-EM) to resolve the structures of integrin αvβ3 in complex with both Rhodostomin and Trimucrin. Researchers performed detailed structural analysis to identify the specific binding interfaces, conformational changes induced upon ligand binding, and key residues involved in the interaction. The investigation aimed to elucidate the atomic-level differences in how these two disintegrins engage with integrin αvβ3 and the resulting impact on receptor conformation.

Structural analysis revealed that both Rhodostomin and Trimucrin adopt a rigid backbone conformation and interact with integrin αvβ3 through three cooperative binding sites. Beyond the conserved RGD interface, Trimucrin uniquely features a cluster of basic residues within its linker region that contributes to binding, while Rhodostomin engages through distinct C-terminal interactions. These subtle differences in binding motifs explain their differential recognition.

Disintegrin binding was found to stabilize αvβ3 in an extended-open conformation, a crucial insight into their enhanced inhibitory action compared to short RGD peptides. Furthermore, the β3-Y110 residue was identified as essential for maintaining the bent, inactive state of αvβ3 in the absence of ligands. These findings provide a high-resolution understanding of how disintegrins achieve more effective and specific integrin inhibition.