Trigger motif

Fig. 4. Schematic diagram of segment IB in intermediate filament chains showing generally conserved features. These include the highly conserved residues L74, L81, and E95 the conserved intra- and interchain ionic interactions represented by solid and dotted lines, respectively the trigger motif (residues 79-91) that acts as a particularly stable region that nucleates coiled-coil formation the site at residue 40 (indicated by an asterisk) of a six heptad insertion in lamin molecules. The entire segment displays a regular disposition of acidic and basic residues, each with a period of about 9.54 residues. These periods are approximately out of phase with one another.

Among the variety of external stimuli that have been described in the previous section for SAMs, enzymes have recently emerged as a pronoising triggering motif for the design of novel responsive polymers. The interest toward enzymatically responsive... 

Krieg, A.M. et al., CpG motifs in bacterial DNA trigger direct B-cell activation, Nature, 374, 546, 1995. 

Frolova LY, Tsivkovskii RY, Sivolobova GF, Oparina NY, Serpinsky Ol, Blinov VM, Tatkov SI, Kisselev LL (1999) Mutations in the highly conserved GGQ motif of class 1 polypeptide release factors abolish ability of human eRFl to trigger peptidyl-tRNA hydrolysis. RNA 5 1014-1020... 

Phosphorylation triggers a second series of events. Phosphorylated amino acids residues act as docking sites for a number of intracellular proteins. These proteins contain their own amino acid motifs that recognize and bind to one or another of the phosphorylated amino acids. Some of these proteins have additional domains that now become activated and bind to other signaling molecules. A complex of proteins is thus assembled at the surface of the cell and specific signaling... 

The Apafl protein has been identified as a central cofactor in cytotoxically-triggered apoptosis. The Apafl protein is homologous to Ced4 protein of C. elegans. It binds to the initiator caspase with the help of a CARD motif A CARD motif is found in the Apafl protein and in various caspases (caspases 1, 2, 4, 5 and 9). 

Binding of the ligand of the Fas receptor triggers clustering of the receptor and association of the cofactor FADD (fas-assodated protein with death domain) which interacts with the receptor via its death domain (DD). Procaspase 8 binds to FADD via a common DED (death effector domain) motif and is thereby also recruited into the Fas-receptor associated complex. Due to the clustering of the proteins, proximity-induced cleavage of procaspase 8 to the mature initiator caspase 8 takes place. This activates the effector caspases and triggers cell death. 

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