期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：4
页码：1873-1878
DOI：10.1073/pnas.0237387100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The integrin X{beta}2 (CD11c/CD18, p150,95) binds ligands through the I domain of the X subunit. Ligands include the complement factor fragment iC3b, a key component in the innate immune defense, which, together with the expression of X{beta}2 on dendritic cells and on other leukocytes, suggests a role in the immune response. We now report the structure of the X I domain resolved at 1.65 A by x-ray crystallography. To analyze structural requirements for ligand binding we made a mutation in the X I domain C-terminal helix, which increased the affinity for iC3b {approx}200-fold to 2.4 {micro}M compared with the wild-type domain affinity of {approx}400 {micro}M. Gel permeation chromatography supported a conformational change between the wild-type and mutated domains. Conservation of allosteric regulation in the X I domain points to the functional importance of this phenomenon.
