Current methods for mapping ligand-protein interactions face challenges in resolving weak yet critical binding events and capturing conformational dynamics, particularly for pleiotropic endogenous hormones such as 17β-estradiol (E2). In this study, we developed a peptide-centric, dose-resolved strategy, termed two-dimensional (2D) peptide-centric local stability assay (PELSA). By integrating peptide-level statistical confidence with dose-response modeling, 2D-PELSA enables highly reliable target identification and the direct estimation of local binding affinities in native cellular environments. In particular, the incorporation of dose-dependent information transforms static proteolysis signatures into quantitative readouts of local structural remodeling, thereby enabling enhanced resolution in capturing subtle structural alterations across proteins, including direct engagement, allosteric regulation, complex regulation, etc. We then demonstrated the versatility of 2D-PELSA by investigating the interactions of 17β-estradiol (E2), a predominant sex hormone that exerts diverse biological functions in both health and disease. Using this approach, we identified 1288 conformotypic E2-responsive peptides and 24 candidate targets with micromolar EC50 values (1-20 M) in BT474 breast cancer cell lysates, which were enriched in the processes of unsaturated and long-chain fatty acid metabolism. Among these, GPX4, a key regulator of ferroptosis, was identified as an E2-engaged protein with an estimated EC50 value of 2.4 M and was downregulated upon micromolar E2 treatment. This interaction was further validated using multiple orthogonal methods based on western blotting and mass spectrometry in both living cells and cell lysates. Integrated proteomic and lipidomic analyses show that chronic micromolar E2 exposure induces extensive lipid metabolic reprogramming and promotes ferroptosis-associated processes, accompanied by increased lipid peroxidation. Consistently, phenotypic analyses showed that micromolar E2 treatment indeed promotes oxidative, iron-dependent cell death. However, this effect was only partially rescued by the ferroptosis inhibitor ferrostatin-1 (Fer-1) and the iron chelator deferoxamine (DFO), indicating the involvement of additional cell death pathways and supporting a multi-target mode of action. Collectively, these findings establish 2D-PELSA as a versatile platform for dissecting ligand-induced structural responses and offer a systems-level perspective on E2 target engagement in complex biological contexts.