Updated project metadata. Antibody-based affinity purification of macromolecular complexes has revolutionized the study of protein-protein interactions. Here, we present AptA-MS (Aptamer Affinity – Mass Spectrometry), a robust strategy using a specific, high-affinity RNA aptamer against GFP to identify novel interactors of a GFP-tagged protein using high resolution MS. AptA-MS offers a high signal-to-noise ratio due to the absence of immunoprecipitation-derived contaminants and allows the identification of post-translational modifications without the need for modification-specific enrichments.