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Pseudokinase domain of Integrin Linked Kinase The pseudokinase domain shows similarity to protein kinases but lacks crucial residues for catalytic activity. ILK contains N-terminal ankyrin repeats, a Pleckstrin Homology (PH) domain, and a C-terminal pseudokinase domain. It is a component of the IPP (ILK/PINCH/Parvin) complex that couples beta integrins to the actin cytoskeleton, and plays important roles in cell adhesion, spreading, invasion, and migration. ILK was initially thought to be an active kinase despite the lack of key conserved residues because of in vitro studies showing that it can phosphorylate certain protein substrates. However, in vivo experiments in Caenorhabditis elegans, Drosophila melanogaster, and mice (ILK-null and knock-in) proved that ILK is not an active kinase. In addition to actin cytoskeleton regulation, ILK also influences the microtubule network and mitotic spindle orientation. The pseudokinase domain of ILK binds several adaptor proteins including the parvins and paxillin. The ILK subfamily is part of a larger superfamily that includes the catalytic domains of protein serine/threonine kinases, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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