Toxin-encoding genes

TRP channels. Some human diseases and important pathological conditions are now being associated with TRP channel dysfunction. At this point, four channelopathies have been identified in which a defect in a TRP channel encoding gene is the direct cause of disease. TRPs also are involved in some systemic diseases because they can be modulated by xenobiotic toxins, irritants, and inflammation products. Other indications of the involvement of TRPs in several diseases come from both the correlation between the level of channel expression to disease symptoms and from the mapping of encoding genes for TRP channel. 

The intrinsic complexity and the multiplicity of cholinergic receptors became evident upon elucidation of their primary structures. In the CNS, at least nine different sequences of a subunits and three different sequences of (3 subunits of the nicotinic receptor have been identified [10, 11]. Expression of the cloned genes encoding certain subunit combinations yields functional receptors with different sensitivities toward various toxins and agonists. 

Fig. 1. Outline of the strategy to construct GST-fused expression plasmids by the in vitro recombination-assisted method. Am, Gm, and Cm are abbreviations for ampicillin-, gentamicin-, and chloramphenicol-resistance, respectively. The figure also indicates the ccdB gene encoding a toxin targeting the co//essential DNA gyrase and the phage X recombination sites (attB, attP, attL, and attR).

Genes encoding M1-M5 receptors were identified in the mid 1980s (Kubo et al., 1986 Bonner et al., 1987) numbers were assigned in the order of discovery. The M5 muscarinic receptor gene was the last to be found. It is present in the brain and viscera, but only in very low concentrations. No selective high-affinity ligands or toxins for the M5 receptor have been found, and no tissues with predominant concentrations of M5 receptors have been identified (Yeomans et al., 2001). 

---