Question

Please describe signal transduction using yeast as an example.

Answer 1

The cellular process in which a chemical or physical signal is transmitted through a cell to trigger a change in the activity or state of a cell is known as signal transduction. This is usually done most commonly by protein phosphorylation which is catalyzed by protein kinases. Signal transducing receptors are of four general classes.

1. Receptors that penetrate the plasma membrane and have intrinsic enzymatic activity or are enzyme associated (Enzyme-linked Receptors)
2. Receptors that are coupled, inside the cell, to G proteins (7-Transmembrane Receptors also known as G protein coupled Receptors)
3. Receptors that are found intracellularly and upon ligand binding directly alter gene transcription (Nuclear Receptors)
4. Ligand-gated ion channels

Yeast have 130 type of kinases. Although they do not have tyrosine kinases. One of the best example of signal transduction in yeast is the yeast mating. Yeast cells identify their mates by cell communication. They have two types of mating cells 'A' and 'a'. They release a chemical factor known as 'a factor'. These type of cells specifically bind with the receptor proteins of nearby cells. Without entering the cell the mating factors cause the cell to grow towards each other. The new cell is formed by fusion and contains genes from both the cells.