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Integrin beta-1-binding protein 1 Phosphotyrosine-binding (PTB) PH-like fold ICAP1 (also called Integrin cytoplasmic domain-associated protein 1) binds specifically to the beta1 integrin subunit cytoplasmic domain and the cerebral cavernous malformation (CCM) protein CCM1. It regulates beta1 integrin-dependent cell migration by affecting the pattern of focal adhesion formation. ICAP1 recruits CCM1 to the cell membrane and activates CCM1 by changing its conformation. Since CCM1 plays role in cardiovascular development, it is hypothesized ICAP1 is involved in vascular differentiation. ICAP-1 has an N-terminal domain that rich in serine and threonine and a C-terminal PTB domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.
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