PMID: 12526797

Authors:

Shimaoka M, Xiao T, Liu JH, Yang Y, Dong Y, Jun CD, McCormack A, Zhang R, Joachimiak A, Takagi J, Wang JH, Springer TA

Title:

Structures of the alpha L I domain and its complex with ICAM-1 reveal a shape-shifting pathway for integrin regulation.

Journal:

Cell. 2003 Jan 10;112(1):99-111.

Abstract:

The structure of the I domain of integrin alpha L beta 2 bound to the Ig superfamily ligand ICAM-1 reveals the open ligand binding conformation and the first example of an integrin-IgSF interface. The I domain Mg2+ directly coordinates Glu-34 of ICAM-1, and a dramatic swing of I domain residue Glu-241 enables a critical salt bridge. Liganded and unliganded structures for both high- and intermediate-affinity mutant I domains reveal that ligand binding can induce conformational change in the alpha L I domain and that allosteric signals can convert the closed conformation to intermediate or open conformations without ligand binding. Pulling down on the C-terminal alpha 7 helix with introduced disulfide bonds ratchets the beta 6-alpha 7 loop into three different positions in the closed, intermediate, and open conformations, with a progressive increase in affinity.