By changing their structural conformation proteins swiftly respond to cellular stimuli and needs. A mass spectrometry (MS)-based method has been introduced to probe protein structural conformations in a whole proteome, which relies on a protease that cuts in a limited time-frame surface-available sites on proteins and such cuts are then read out by MS, hence its name limited proteolysis (LiP)-MS. LiP-MS works on lysates in which conformations of proteins may not reflect those in living cells because of inevitable protein denaturation during cell lysis. We propose a conformational proteomics method that directly works in living cells, this by expressing a protease of which the activity is tightly controlled. Once established, we will apply this method to study the influence of N-terminal acetylation on protein conformations and ligand-induced conformational changes of the glucocorticoid receptor.