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KMID : 0578320100300030227
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Molecules and Cells
2010 Volume.30 No. 3 p.227 ~ p.234
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Characterization of the Residues of αX I-Domain and ICAM-1 Mediating Their Interactions
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Choi Jeong-Suk
Choi Jea-Sun
Nham Sang-Uk
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Abstract
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Integrin αXβ2 performs a significant role in leukocyte functions including phagocytosis and migration, and binds to a variety of ligands, including fibrinogen, iC3b, and ICAM-1. A particular domain of the α subunit of the integrin - the αX I-domain - is a ligand binding site, and the interaction of the αX I-domain and ICAM-1 on the endothelium is an important step in leukocyte extravasation. In order to elucidate the structural aspects of this interaction, we defined the moieties of the αX and ICAM-1 relevant to their interaction in this study. It was determined that the ICAM-1 binding sites of the αX I-domain were located in the α3α4, βDα5, and βFα7 loops at the top surface of the I-domain. The residues Q202, K242, K243, E298 and D299 on these loops were crucial for the recognition of ICAM-1. Among these residues, K242 and K243 on the βDα5 loop were found to be the most salient, thereby suggesting an ionic interaction between these proteins. Domain 3 of ICAM-1 was identified as a primary binding site for the αX I-domain. Two regions of domain 3 (D229QRLNPTV and E254DEGTQRL) perform critical functions in the binding of the αX I-domain. Especially, the residue E254DEG, is most important with regard to the αX I-domain.
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KEYWORD
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αXβ2, binding, ICAM-1, I-domain, integrin
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