pH-Responsive Probe for β-Lactamase-based Protein Tag in Fluorescence Imaging of Receptor Endocytosis

Abstract Fluorescence imaging of the local pH environment surrounding proteins offers an understanding of cellular processes, including receptor endocytosis. We herein develop a pH-responsive fluorescent β-lactamase inhibitor for protein labeling via a genetically encodable β-lactamase tag. Our probe enabled time-lapse monitoring of pH decrease during internalization of membrane receptor proteins in living cells.