NeissLock provides an inducible protein anhydride for covalent targeting of endogenous proteins

Mapping protein-protein interactions by mass spectrometry

Protein-protein interactions (PPIs) are essential for numerous biological activities, including signal transduction, transcription control, and metabolism. They play a pivotal role in the organization and function of the proteome, and their perturbation is associated with various diseases, such as cancer, neurodegeneration, and infectious diseases. Recent advances in mass spectrometry (MS)-based protein interactomics have significantly expanded our understanding of the PPIs in cells, with techniques that continue to improve in terms of sensitivity, and specificity providing new opportunities for the study of PPIs in diverse biological systems. These techniques differ depending on the type of interaction being studied, with each approach having its set of advantages, disadvantages, and applicability. This review highlights recent advances in enrichment methodologies for interactomes before MS analysis and compares their unique features and specifications. It emphasizes prospects for further improvement and their potential applications in advancing our knowledge of PPIs in various biological contexts.

NeissLock provides an inducible protein anhydride for covalent targeting of endogenous proteins

The Neisseria meningitidis protein FrpC contains a self-processing module (SPM) undergoing autoproteolysis via an aspartic anhydride. Herein, we establish NeissLock, using a binding protein genetically fused to SPM. Upon calcium triggering of SPM, the anhydride at the C-terminus of the binding protein allows nucleophilic attack by its target protein, ligating the complex. We establish a computational tool to search the Protein Data Bank, assessing proximity of amines to C-termini. We optimize NeissLock using the Ornithine Decarboxylase/Antizyme complex. Various sites on the target (α-amine or ε-amines) react with the anhydride, but reaction is blocked if the partner does not dock. Ligation is efficient at pH 7.0, with half-time less than 2 min. We arm Transforming Growth Factor-α with SPM, enabling specific covalent coupling to Epidermal Growth Factor Receptor at the cell-surface. NeissLock harnesses distinctive protein chemistry for high-yield covalent targeting of endogenous proteins, advancing the possibilities for molecular engineering.

Covalent conjugation of endogenous protein complexes offers many opportunities for fundamental and clinical research. Based on a bacterial protein domain that forms a reactive anhydride in the presence of Ca²⁺, the authors here develop a system that enables the covalent capture of endogenous binding partners.