3v4p
crystal structure of a4b7 headpiece complexed with Fab ACT-1
Structural highlights
FunctionITB7_HUMAN Integrin alpha-4/beta-7 (Peyer patches-specific homing receptor LPAM-1) is an adhesion molecule that mediates lymphocyte migration and homing to gut-associated lymphoid tissue (GALT). Integrin alpha-4/beta-7 interacts with the cell surface adhesion molecules MADCAM1 which is normally expressed by the vascular endothelium of the gastrointestinal tract. Interacts also with VCAM1 and fibronectin, an extracellular matrix component. It recognizes one or more domains within the alternatively spliced CS-1 region of fibronectin. Interactions involves the tripeptide L-D-T in MADCAM1, and L-D-V in fibronectin. Binds to HIV-1 gp120, thereby allowing the virus to enter GALT, which is thought to be the major trigger of AIDS disease. Interaction would involve a tripeptide L-D-I in HIV-1 gp120. Integrin alpha-E/beta-7 (HML-1) is a receptor for E-cadherin. Publication Abstract from PubMedThe lymphocyte homing receptor integrin alpha(4)beta(7) is unusual for its ability to mediate both rolling and firm adhesion. alpha(4)beta(1) and alpha(4)beta(7) are targeted by therapeutics approved for multiple sclerosis and Crohn's disease. Here, we show by electron microscopy and crystallography how two therapeutic Fabs, a small molecule (RO0505376), and mucosal adhesion molecule-1 (MAdCAM-1) bind alpha(4)beta(7). A long binding groove at the alpha(4)-beta(7) interface for immunoglobulin superfamily domains differs in shape from integrin pockets that bind Arg-Gly-Asp motifs. RO0505376 mimics an Ile/Leu-Asp motif in alpha(4) ligands, and orients differently from Arg-Gly-Asp mimics. A novel auxiliary residue at the metal ion-dependent adhesion site in alpha(4)beta(7) is essential for binding to MAdCAM-1 in Mg(2+) yet swings away when RO0505376 binds. A novel intermediate conformation of the alpha(4)beta(7) headpiece binds MAdCAM-1 and supports rolling adhesion. Lack of induction of the open headpiece conformation by ligand binding enables rolling adhesion to persist until integrin activation is signaled. Structural specializations of alpha(4)beta(7), an integrin that mediates rolling adhesion.,Yu Y, Zhu J, Mi LZ, Walz T, Sun H, Chen J, Springer TA J Cell Biol. 2012 Jan 9;196(1):131-46. PMID:22232704[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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