Adaptation of the Protocol for the Isolation of Biotinylated Protein Complexes for Drosophila melanogaster Tissues.

Proximity biotinylation, which utilizes various biotin ligating enzymes (BioID, TurboID, etc.), is widely used as a powerful tool for identifying novel protein-protein interactions. However, this method has a significant limitation: the use of streptavidin on beads for enriching biotinylated proteins often results in a high background of peptides from streptavidin itself, which interferes with identification by peptide mass fingerprinting. This limitation makes it practically impossible to study samples containing a small amount of material, such as individual insect tissues. In this study, we compared different precipitation and elution conditions for the purification of biotinylated proteins from protein extracts of Drosophila melanogaster S2 cells. We found that biotinylated proteins can be purified using anti-biotin antibodies, although with lower efficiency than streptavidin-based resin. We also demonstrated that protease-resistant streptavidin (prS), previously tested in mammalian cells, can be used effectively to purify biotinylated proteins from tissues of D. melanogaster. In our experiments, prS showed precipitation efficiency comparable to regular streptavidin but generated a lower background in peptide fingerprinting. To further demonstrate the applicability of prS for studying protein-protein interactions in D. melanogaster tissues, we carried out experiments to identify interaction partners of the ecdysone receptor (EcR) in D. melanogaster ovarian tissue using TurboID-based proximity biotinylation. As a result, EcR was found to interact with both previously described and novel protein partners in Drosophila ovaries.