Download MendeleyTuning the Sensitivity of Genetically Encoded Fluorescent Potassium Indicators through Structure-Guided and Genome Mining Strategies.
Torres Caban, C.C., Yang, M., Lai, C., Yang, L., Subach, F.V., Smith, B.O., Piatkevich, K.D., Boyden, E.S.(2022) ACS Sens 7: 1336-1346
- PubMed: 35427452
- DOI: https://doi.org/10.1021/acssensors.1c02201
- Primary Citation of Related Structures:
7PVC - PubMed Abstract:
Genetically encoded potassium indicators lack optimal binding affinity for monitoring intracellular dynamics in mammalian cells. Through structure-guided design and genome mining of potassium binding proteins, we developed green fluorescent potassium indicators with a broad range of binding affinities. KRaION1 (K + ratiometric indicator for optical imaging based on mNeonGreen 1), based on the insertion of a potassium binding protein, Kbp, from E. coli (Ec-Kbp) into the fluorescent protein mNeonGreen, exhibits an isotonically measured K d of 69 ± 10 mM (mean ± standard deviation used throughout). We identified Ec-Kbp's binding site using NMR spectroscopy to detect protein-thallium scalar couplings and refined the structure of Ec-Kbp in its potassium-bound state. Guided by this structure, we modified KRaION1, yielding KRaION1/D9N and KRaION2, which exhibit isotonically measured K d 's of 138 ± 21 and 96 ± 9 mM. We identified four Ec-Kbp homologues as potassium binding proteins, which yielded indicators with isotonically measured binding affinities in the 39-112 mM range. KRaIONs functioned in HeLa cells, but the K d values differed from the isotonically measured case. We found that, by tuning the experimental conditions, K d values could be obtained that were consistent in vitro and in vivo . We thus recommend characterizing potassium indicator K d in the physiological context of interest before application.
Organizational Affiliation:
McGovern Institute for Brain Research, MIT, Cambridge, Massachusetts 02139, United States.
