Lanthanide protein biosensors with a single ion-binding site

Abstract

Abstract Rising demand for rare earth elements, including lanthanides (Lns), has intensified environmental pressures and supply-chain vulnerabilities, motivating the development of bio-based methods for their extraction and separation. However, the lack of high-throughput assays for analysing the selectivity of lanthanide-binding proteins remains a key bottleneck in engineering bio-based Ln-extraction systems. Here, we report the development of high-throughput assays based on Ln-responsive protein biosensors. These β-lactamase-based biosensors contain receptors with a single Ln-binding site derived from either lanmodulin or the AI-designed protein RF2. We established multiplexed colourimetric assays that quantify biosensor activity and selectivity in vitro and in the periplasm of E. coli . We further demonstrate that E. coli cells expressing these biosensors exhibit Ln-dependent survival in the presence of β-lactam antibiotics. These platforms enable large-scale testing of Ln biosensors and Ln-binding proteins.