Transducer protein

Transmembrane Signaling. Figure 2 Membrane topology of receptors that are associated with effector proteins. Upon binding to their cognate ligands (cyan), receptor proteins without intramolecularly linked effector domain couple via transducer proteins (yellow) to or directly recruit and activate effector proteins (red). Notch receptors release their transducer domains upon proteolytic cleavage, a, p and y stand for G-protein a-, p- and y-subunits, respectively. 

Therefore, investigators have shown considerable interest in the adoption of the Langmuir-Blodgett technique, or its modifications, to make molecular electronic devices using, in particular, as an active component, a light-transducing protein, such as BR. In fact, the ability of BR to form thin films with excellent optical properties and the intrinsic properties themselves make it an outstanding candidate for use in optically coupled devices. 

Wood, K. W Samecki, C., Roberts, T. M and Blenis, J. (1992). ras mediates nerve growth factor receptor modulation of three signal-transducing protein kinases MAP kinase, Raf-1, and RSK. Cell 68 1041-1050. 

The fluidity of lipid bilayers permits dynamic interactions among membrane proteins. For example, the interactions of a neurotransmitter or hormone with its receptor can dissociate a transducer protein, which in turn will diffuse to interact with other effector proteins (Ch. 19). A given effector protein, such as adenylyl cyclase, may respond differently to different receptors because of mediation by different transducers. These dynamic interactions require rapid protein diffusion within the plane of the membrane bilayer. Receptor occupation can initiate extensive redistribution of membrane proteins, as exemplified by the clustering of membrane antigens consequent to binding bivalent antibodies [8]. In contrast to these examples of lateral mobility, the surface distribution of integral membrane proteins can be fixed by interactions with other proteins. Membranes may also be partitioned into local spatial domains consisting of networks... 

Membrane-associated receptors are linked to transducing proteins (like G-proteins) in the inner portion of the membrane. G-protein coupled receptor (GPCR) families comprise a major class of the receptors that are pharmacologically relevant, such as muscarinic acetyl choline receptors, adrenoceptors, dopamine receptors, serotonine, opiate, peptide hormone, purinerg receptors, and also sensory chemoreceptors. A large variety of subtypes are described in the pharmacological literature. 

Conversely, in the tyrosine kinase pathway the effector enzyme is either an intracellular portion of the cell-surface receptor or directly coupled to it without the assistance of a transducer protein. 

Denhardt DT. Signal-transducing protein phosphorylation cascades mediated by Ras/Rho proteins in the mammalian cell the potential for multiplex signalling. B/oc/jeraJ 1996 318 729-747. 

As an attempt to connect the first discussion, which was concerned with diffusion-reaction coupling, with Dr. Williams presentation of enzymes as dynamic systems, I wanted to direct attention to a number of specific systems. These are the energy-transducing proteins that couple scalar chemical reactions to vectorial flow processes. For example, I am thinking of active transport (Na-K ATPase), muscular contraction (actomyosin ATPase), and the light-driven proton pump of the well-known purple... 

Wodicka, L. M. and Morse, D. E., cDNA sequences reveal mRNAs for two Ga signal transducing proteins from larval cilia, Biol. Bull., 180, 1991. 

Signal transducing proteins general subunit structure... 

Gedrich, R. W., Gilfillan, M. C., Duckett, C. S., Van Dongen, J. L., and Thompson, C. B. (1996). CD30 contains two binding sites with different specificities for members of the tumor necrosis factor receptor-associated factor family of signal transducing proteins./. Biol. Chem. 271, 12852-12858. 

Sato, T., Irie, S., and Reed, J. C. (1995). A novel member of the TRAP family of putative signal transducing proteins binds to the cytosolic domain of CD40. FEBS Lett. 358, 113-118. 

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