Final answer:
The yeast two-hybrid system reveals protein-protein interactions by utilizing the activation of a reporter gene. A bait protein is attached to a DNA-binding domain and a prey protein to an activator domain; reporter gene transcription indicates interaction. The system benefits from the highly conserved nature of signaling mechanisms in yeasts and other eukaryotes.
Step-by-step explanation:
The yeast two-hybrid system takes advantage of the activation of a reporter gene to reveal protein-protein interactions.
When studying interactions between two proteins, known as the bait and prey, the system utilizes a transcription factor that is split into two different domains: a DNA-binding domain (BD) and an activator domain (AD). The bait protein is fused to the BD, while the prey protein is fused to the AD.
A reporter gene is placed downstream of a promoter that the BD can bind to, but without AD binding, the promoter alone does not initiate transcription.
If the bait protein interacts with the prey protein, the AD is brought into proximity with the BD, allowing for the initiation of transcription of the reporter gene. This transcription is observable and indicates that the two proteins are capable of interacting.
Importantly, if the prey doesn't 'catch' the bait, no transcription occurs, providing a clear binary readout for protein-protein interaction.
Additionally, signaling in yeast, including the use of G-protein coupled receptors, is evolutionarily conserved and shares similarities with signaling mechanisms in multicellular organisms, such as insulin signaling in humans. This makes the yeast two-hybrid system a valuable tool for understanding molecular interactions that are relevant across different species.