Signal transduction
An estimated
21% of the human genome prouducts function in signal
transduction, by which information about the
extracellular environment is conveyed to the cell for an
appropriate response. In this example, in the absence of
an external signal, a cell-surface receptor
maintain an uninduced conformation and the transducer
protein is inactive. Upon induction by an extracellular
signal, the receptor changes comformation so as to
trigger phophorylation of the transducer
protein. The change of state of the transducer goes on
to function in in further signal transduction, for
example by binding another protein.
[My daughters' shape toy is also an example of signal transduction. Removal of any shape from the board exposes a photocell to light. Replacement of the shape closes the photocell, which causes a sound appropriate to the shape. That is, the light signal is transduced to a sound response].
Transduction may be altered in several ways. A constitutive mutant causes the receptor to be permanently in an "on" state, such that transduction occurs in the absence of a signal. Alternatively, an non-iducible mutant may modity the receptor such that it is unable to respond to the signal, such that transduction does not occur.
[My daughters' shape toy is also an example of signal transduction. Removal of any shape from the board exposes a photocell to light. Replacement of the shape closes the photocell, which causes a sound appropriate to the shape. That is, the light signal is transduced to a sound response].
Transduction may be altered in several ways. A constitutive mutant causes the receptor to be permanently in an "on" state, such that transduction occurs in the absence of a signal. Alternatively, an non-iducible mutant may modity the receptor such that it is unable to respond to the signal, such that transduction does not occur.
Figure after © 2012 TA Brown, Introduction to Genetics (1st ed.); additional text © 2012 by Steven M. Carr