Transmembrane receptor Intracellular domain

FIGURE 24-6 Schematic structures of receptor protein tyrosine kinase (RPTK) families. RPTKs can be divided into different families according to the structural features in the extracellular domain. Following the extracellular domain are the transmembrane and intracellular domains the latter contains the catalytic domain. (From reference [5], with permission of Nature. Nature 2001.)... 

Model of the insulin receptor. The receptor contains two a- and two /1-subunits, held together by disulfide linkages. The a-subunits are entirely extracellular and contain the insulin binding site, The jS-subunits have transmembrane and intracellular domains. Both autophosphorylation and tyrosine kinase activity reside in the -subunit and are markedly enhanced upon insulin binding. 

Hybrid. Suppose that, through genetic manipulations, a chimeric receptor is produced that consists of the extracellular domain ot the insulin receptor and the transmembrane and intracellular domains of the hlGP receptor. Cells expressing this receptor are expo.sed to insulin and the level ot phosphorylation of the chimeric receptor is examined. What would you expect to observe and why What would you expect to observe if these cells were exposed to EGF ... 

Figure 13.1 The basic organization of a membrane receptor molecule consists of an extracellular domain, a transmembrane region, and an intracellular domain.

Besides cytoplasmic protein kinases, membrane receptors can exert protein kinase activity. These so-called receptor tyrosine kinases (RTK) contain a ligandbinding extracellular domain, a transmembrane motif, and an intracellular catalytic domain with specificity for tyrosine residues. Upon ligand binding and subsequent receptor oligomerization, the tyrosine residues of the intracellular domain become phosphory-lated by the intrinsic tyrosine kinase activity of the receptor [3, 4]. The phosphotyrosine residues ftmction as docking sites for other proteins that will transmit the signal received by the RTK. 

The IL-ls induce their characteristic biological activities by binding to specific cell surface receptors present on sensitive cells. Two distinct receptors, type I and II, have been identified. Both IL-la and IL-ip can bind both receptors. The type I receptor is an 80 kDa transmembrane glycoprotein. It is a member of the IgG superfamily. This receptor is expressed predominantly on fibroblasts, keratinocytes, hepatocytes and endothelial cells. The type II receptor is a 60 kDa transmembrane glycoprotein, expressed mainly on B-lymphocytes, bone marrow cells and polymorphonuclear leukocytes. It displays a very short (29 amino acid) intracellular domain,... 

FIGURE 24-10 Schematic structures of nonreceptor protein tyrosine phosphatases (NRPTPs) and receptor protein tyrosine phosphatases (RPTPs). NRPTPs contain a catalytic domain and various regulatory domains. RPTPs are composed of an extracellular domain, a transmembrane domain and an intracellular domain with one or two catalytic domains. Like receptor protein tyrosine kinases, the structural features of the extracellular domains divide the RPTPs into different families. (With permission from reference [12]). 

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