Final answer:
The main assay for investigating protein interactions in the Interactive database is the Yeast two-hybrid system, which detects protein-protein or protein-DNA interactions.
Step-by-step explanation:
The primary assay used to investigate protein interactions in the Interactive database is the Yeast two-hybrid system. This system is a molecular biology technique used to discover protein-protein interactions by testing for physical interactions between two proteins or a protein and a DNA molecule.
The mass spectrometry technique mentioned as another option is indeed a fundamental technique for protein analysis, allowing for identification and characterization of proteins; however, it is not explicitly designed for studying protein interactions. Instead, mass spectrometry helps in analyzing very small samples of protein and can be used in conjunction with other techniques, such as the yeast two-hybrid system or protein microarrays, to build a broader understanding of protein functions and interactions.
The primary assay used to investigate protein interactions in the Interactive database is the Yeast two-hybrid system. This technique involves the fusion of a DNA-binding domain to one protein and a transcriptional activation domain to another protein of interest. When these two proteins interact, they reconstitute a functional transcription factor, allowing the activation of reporter genes that can be detected.