Ligand induced association

Ligand binding to both cytokine receptors and RTKs triggers formation of functional dimeric receptors. In some cases, the ligand induces association of two monomeric... 

Slow transitions produced by enzyme isomerizations. This behavior can lead to a type of cooperativity that is generally associated with ligand-induced conformational changes . A number of enzymes are also known to undergo slow oligomerization reactions, and these enzymes may display unusual kinetic properties. If this is observed, it is advisable to determine the time course of enzyme activation or inactivation following enzyme dilution. See Cooperativity Bifurcation Theory Lag Time... 

Fukui, M., Imamura, R., Umemura, M., Kawabe, T., Suda, T. Pathogen-associated molecular patterns sensitize macrophages to Fas ligand-induced apoptosis and IL-1 beta release. J Immunol 171 (2003) 1868-1874. 

For TRAF recruitment, since each receptor peptide contacts one TRAP domain only, avidity is the only factor that contributes to enhanced affinity of TRAFs for activated receptors. Due to the lack of structural information on DD interactions, it is not known whether ligand-induced receptor recruitment of FADD and TRADD (Hsu et al, 1996b) is also purely driven by avidity or the intracellular DD of the receptors also form composite binding sites for FADD and TRADD upon receptor activation. In keeping with the latter scenario, a protein known as silencer of death domains (SODD) (Jiang et al, 1999) has been shown to associate with the intracellular DD of TNF-Rl and get released upon ligand stimulation to activate the receptor. 

The chemotaxis receptors that do not bind chemokines also form dimers under certain conditions, but have not yet been found to undergo ligand-induced changes in oligomeric state. The G5a receptor is proposed to constitutively dimerize by association of respective TMIV domains, or possibly an interaction between TMl and TMII (Klco et at, 2003). For this receptor, no evidence yet exists to support ligand-induced dimerization... 

Some ligands induce dimerization of the receptors to which they bind. Such a receptor contains an extracellular domain that binds the ligand, a transmembrane region, and a cytosolic domain that either binds or contains a protein kinase. The growth-hormone receptor participates in an example of this type of signal-transduction pathway. Dimerization of the receptor activates Janus kinase 2, a protein kinase associated with the intracellular part of the receptor. The kinase, in turn, phosphorylates and activates a transcription factor called STAT5. 

The behaviour of binary alloys with respect to catalysis is generally interpreted in terms of either the geometric ensemble effect , associated with the number of nearest neighbours of a given element for the catalytic reaction to occur [3-5] or to the electronic ligand effect , associated to the mutual electronic interaction between the associated elements. In addition, the influence of strains induced on surface atoms has also to be considered for binary alloys when the two partners have different atomic radii. The effect will strongly depend upon the surface composition, and upon the epitaxial relationsship between the outer atomic layer and the substrate layers. Therefore, one has to know precisely the local concentration and atomic arrangement of both components of the alloy at the outermost surface, and in the sublayer. 

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