ABSTRACT
Many signal-transducing receptors are plasma membrane proteins that bind specific extracellular molecules, such as growth factors, hormones, or neurotransmitters, and then transmit to the cell’s interior a signal that elicits a specific response. These responses are usually cascades of enzymatic reactions giving rise to many different effects within the cell, including changes in gene expression. Interference with receptor-signaling systems can therefore have drastic consequences. For example, oncogene products that simulate the function of receptors or their associated signal transmitters cause the loss of cellular growth control.
