PMID: 18691975

 

    Legend: Sugar

Title : An unusual allosteric mobility of the C-terminal helix of a high-affinity alphaL integrin I domain variant bound to ICAM-5

Abstract :

1. Integrins are cell surface receptors that transduce signals bidirectionally across the plasma membrane
2. The key event of integrin signaling is the allosteric regulation between its ligand-binding site and the C-terminal helix (alpha7) of integrin's inserted (I) domain
3. A significant axial movement of the alpha7 helix is associated with the open, active conformation of integrins
4. We describe the crystal structure of an engineered high-affinity I domain from the integrin alpha(L )beta(2) (LFA-1) alpha subunit in complex with the N-terminal two domains of ICAM-5 , an adhesion molecule expressed in telencephalic neurons
5. The finding that the alpha7 helix swings out and inserts into a neighboring I domain in an upside-down orientation in the crystals implies an intrinsically unusual mobility of this helix
6. This remarkable feature allows the alpha7 helix to trigger integrin's large-scale conformational changes with little energy penalty
7. It serves as a mechanistic example of how a weakly bound adhesion molecule works in signaling