Sensory transduction systems

Charles, T.C. Nester, E.W. A chromosomally encoded two-component sensory transduction system is required for virulence of Agrobacterium tumefaciens. J. Bacteriol., 175, 6614-6625 (1993)... 

All cells appear to have a complex thermostat-hke control system for sensing copper status. Various setpoints must exist in the thermostat system to achieve copper homeostasis. Distinct Cu sensory/transduction systems respond to the various setpoints. Future research will be needed to establish the signal sensed and what determines the setpoint of the cellular copper thermostat. 

M. mnthus development. The key to bacterial coordinated behavior resides in the ability of a cell to receive, interpret, and respond to these signals. Relaying the information may require direct contact between the donor and the recipient cells or it may be carried out from a distance, i.e., by means of diffusible molecules, which are detected through their interaction with specific receptors. As discussed in Chapter 3, bacterial chemotaxis is the most completely understood of the bacterial sensory transduction systems. While the role of chemotaxis in intercellular communication is still not clear, in some cases, mutants deleted for chemotaxis genes fail to carry out one or another of the processes mentioned above. Components of the chemotaxis system seem to play a role in swarming motility, pattern formation, and myxobacterial development. In fact, it appears that certain chemotaxis functions have been recruited by certain species to mediate intercellular communication. In this chapter, we review some examples, and provide evidence as well as hypotheses concerning a role for proteins and systems involved in chemotaxis in multicellular behavior. 

Besides these shortcomings the bluelight receptor and sensory transduction problem is recently being attacked on the basis of completely artificial flavin/membrane systems. These appear to provide well-defined model systems to study anisotropic flavin (photo-) chemistry. This, in turn, is an essential prerequisite which allows the primary photo-events of physiological bluelight reception to be imitated and elucidated. 

Chemosensory neurons of the vomeronasal system are narrowly tuned to specific chemical cues, and utilize a unique mechanism of sensory transduction 824... 

The intrinsic transient delay and nonlinearity in the transduction of chemical signals are undesirable from an automatic control perspective. On the other hand, they may represent neural preprocessing in the sensory nervous system. Such transformations in the feedback path may have important bearing on the controller s ability to achieve the control objective. 

Taste-active chemicals react with receptors on the surface of sensory cells in the papillae causing electrical depolarization, ie, drop in the voltage across the sensory cell membrane. The collection of biochemical events that are involved in this process is called transduction (15,16). Not all the chemical steps involved in transduction are known however, it is clear that different transduction mechanisms are involved in different taste quaUties different transduction mechanisms exist for the same chemical in different species (15). Thus the specificity of chemosensory processes, ie, taste and smell, to different chemicals is caused by differences in the sensory cell membrane, the transduction mechanisms, and the central nervous system (14). 

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