Coming to grips with integrin binding to ligands

Area of Science:

• Cell Biology
• Structural Biology
• Biochemistry

Background:

• Integrins are crucial alphabeta heterodimeric cell-surface receptors for nucleated cell survival and function.
• They recognize aspartic-acid- or glutamic-acid-based motifs in ligands, with binding typically dependent on divalent cations and conformation.
• A structural basis for integrin-ligand binding specificity has been lacking.

Purpose of the Study:

• To provide an atomic basis for cation-mediated binding of aspartic-acid-based ligands to integrins.
• To model other integrins with larger physiologic ligands.
• To gain insights into the molecular basis of integrin ligand binding specificity and its regulation.

Main Methods:

• Analysis of recently reported crystal structures of an integrin extracellular segment.
• Structural comparison of the integrin in its unliganded state and complexed with an Arg-Gly-Asp (RGD) ligand.
• Modeling of other integrins in complex with larger physiologic ligands based on existing structural data.

Main Results:

• Crystal structures provide an atomic basis for divalent cation-mediated binding of aspartic-acid-based ligands to integrins.
• These structures serve as a foundation for modeling other integrin-ligand interactions.
• New insights into the molecular mechanisms of ligand binding specificity and its regulation by integrin activation are provided.

Conclusions:

• The atomic structures elucidate the cation-dependent recognition of specific amino acid motifs by integrins.
• Structural models offer a framework for understanding diverse integrin-ligand interactions and specificity.
• Integrin activation-driven conformational changes are key to regulating ligand binding specificity.