Adaptor molecule

An additional pathway leading to very efficient EFN-(3 responses involves one of the Toll-like-recqDtors (TLR), TLR3 which also senses dsRNA and is mainly expressed in dendritic cells (DC) and macrophages. Signal transduction then proceeds via the adaptor molecule TICAM/TRIF associated with the TER.-domain of... 

CpG-rich dsDNA, respectively. Following activation, these TLRs bind to a complex consisting of the specific adaptor molecule MyD88, TRAF6, and the kinases IRAK-1 and IRAK-4. ERF-7, which is also part of this complex is then phosphorylated by IRAK-1, forms dimers and shuttles to the nucleus to specifically activate the EFN-a promoter. 

For enzyme coupled receptors, activation of the receptor turns the receptor itself into an active enzyme. This activity may belong to the receptor itself, but sometimes activation of the receptor recruits and activates a separate enzyme through adaptor molecules (Fig. 9-3). A common mechanism of activation of these receptors involves dimerization. The signal molecule causes individual molecules of the receptor to associate with themselves in the membrane. Once dimerized, the receptors become activated and gain enzyme activity. 

Recruitment of Grb2 to the membrane activates the MAPK pathway. Grb2 is an adaptor molecule carrying one SH2 and two SH3 domains (Fig. 24-4). The Grb2 SH2 domain recognizes the tyrosine-phosphorylated moiety on certain RPTKs, such as EGFR (Fig. 24-8), and anchors... 

PTKs are monomeric in the active form, and consist of an extracellular binding domain, single membrane-associated a-helix and cytosolic domain with the kinase activity. Ligand binding induces dimerization and autophosphorylation that enables binding to adaptor molecules. These molecules connect the receptor to the signal transmitting biopolymers. 

Whereas DNA is mostly located in the nucleus of cells in higher organisms (with some also in mitochondria and in plant chloroplasts), RNA comes in three major and distinct forms, each of which plays a crucial role in protein biosynthesis in the cytoplasm. These are, respectively, ribosomal RNA (rRNA), which represents two-thirds of the mass of the ribosome, messenger RNA (mRNA), which encodes the information for the sequence of proteins, and transfer RNAs (tRNAs) which serve as adaptor molecules, allowing the 4-letter code of nucleic acids to be translated into the 20-letter code of proteins. These latter molecules contain a substantial number of modified bases, which are introduced enzymatically. 

DNA directs its own replication and its transcription into RNA that, in turn, directs its translation into protein. tRNA is the adaptor molecule that mediates the interaction between mRNA and the encoded amino acid. 

The activated receptor can also associate with adaptor molecules, which serve as coupling elements for further signal proteins. 

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