Fig. 1: Engineering fluorogenic reporters for imaging of spike–ACE2 interaction in cells.
From: Fluorogenic reporter enables identification of compounds that inhibit SARS-CoV-2
a, Schematic of the PPI reporter SURF based on a split fluorescent protein. X and Y represent two proteins of interest. b, Schematic of structure-based design of an initial SURF reporter for imaging of spike–ACE2 interaction. c,d, Fluorescence images (c) and quantification (d) of the initial and improved SURF reporters in imaging of spike–ACE2 interaction. SURF brightness was improved 270-fold via protein engineering by ACE2 truncation and mCherry insertion. c, Scale bars, 20 µm. d, Norm. SURF Fluo.: normalized SURF fluorescence. SRBD (residues 319–541) truncations refer (left to right) to: SRBD (333–541) with ACE2 (1–615, 10–615 and 17–615) and SRBD (333–518) with ACE2 (1–615, 10–615 and 17–615). Data presented as mean ± s.d. (n = 5). e, The final SURF reporter, SRBD::ΔACE2 SURF, is bright and reversible. ΔACE2, truncated ACE2 (residues 17–615); IFP2, a near-infrared fluorescent protein. Experiments were repeated three times independently, with similar results.
