The allosteric coupling between activation and inactivation processes is a common feature observed in K channels. Particularly, in the prokaryotic KcsA channel the K conduction process is controlled by the inner gate, which is activated by acidic pH, and by the selectivity filter (SF) or outer gate, which can adopt non-conductive or conductive states. In a previous study, a single tryptophan mutant channel (W67 KcsA) enabled us to investigate the SF dynamics using time-resolved homo-Förster Resonance Energy Transfer (homo-FRET) measurements. Here, the conformational changes of both gates were simultaneously monitored after labelling the G116C position with tetramethylrhodamine (TMR) within a W67 KcsA background. At a high degree of protein labeling, fluorescence anisotropy measurements showed that the pH-induced KcsA gating elicited a variation in the homo-FRET efficiency among the conjugated TMR dyes (TMR homo-FRET), while the conformation of the SF was simultaneously tracked (W67 homo-FRET). The dependence of the activation p of the inner gate with the ion occupancy of the SF unequivocally confirmed the allosteric communication between the two gates of KcsA. This simple TMR homo-FRET based ratiometric assay can be easily extended to study the conformational dynamics associated with the gating of other ion channels and their modulation.
Download full-text PDF |
Source |
---|---|
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8584343 | PMC |
http://dx.doi.org/10.3390/ijms222111954 | DOI Listing |
Biochim Biophys Acta Biomembr
February 2024
University of Strasbourg/CNRS, UMR7177, Strasbourg Institute of Chemistry, Membrane Biophysics and NMR, 67000 Strasbourg, France; Institut Universitaire de France, 75231 Paris, France.
The heptad repeat 1 and 2 (HR1, HR2) regions in the spike protein of SARS-CoV 2 play a key role in the fusogenic mechanism of the virus with the host cell. During the fusion process they are thought to rearrange into an interdomain multimer. Functional fragments of the heptad repeat 1 and 2 regions in the spike protein of SARS-CoV 2 were chemically synthesized, labeled with nitrofurazone (NBD) and their interactions investigated by fluorescence spectroscopy.
View Article and Find Full Text PDFMol Biol Cell
May 2023
Cell Biology Group, National Centre for Biological Sciences, UAS-GKVK Campus, Tata Institute for Fundamental Research, Bangalore 560065, India.
Quantitative fluorescence emission anisotropy microscopy reveals the organization of fluorescently labeled cellular components and allows their characterization in terms of changes in either rotational diffusion or homo-Förster's energy transfer characteristics in living cells. These properties provide insights into molecular organization, such as orientation, confinement, and oligomerization in situ. Here we elucidate how quantitative measurements of anisotropy using multiple microscope systems may be made by bringing out the main parameters that influence the quantification of fluorescence emission anisotropy.
View Article and Find Full Text PDFEur J Cell Biol
June 2023
Cancer Cell Biology and Drug Discovery group, Department of Life Sciences and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg. Electronic address:
The small GTPase Ras is frequently mutated in cancer and a driver of tumorigenesis. The recent years have shown great progress in drug-targeting Ras and understanding how it operates on the plasma membrane. We now know that Ras is non-randomly organized into proteo-lipid complexes on the membrane, called nanoclusters.
View Article and Find Full Text PDFInt J Mol Sci
August 2022
Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), and Instituto de Biología Molecular y Celular (IBMC), Universidad Miguel Hernández, 03202 Elche, Spain.
Y55W mutants of non-selective NaK and partly K-selective NaK2K channels have been used to explore the conformational dynamics at the pore region of these channels as they interact with either Na or K. A major conclusion is that these channels exhibit a remarkable pore conformational flexibility. Homo-FRET measurements reveal a large change in W55-W55 intersubunit distances, enabling the selectivity filter (SF) to admit different species, thus, favoring poor or no selectivity.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
August 2022
Department of Bioengineering, Rice University, Houston, TX 77005.
Bacteria utilize two-component system (TCS) signal transduction pathways to sense and adapt to changing environments. In a typical TCS, a stimulus induces a sensor histidine kinase (SHK) to phosphorylate a response regulator (RR), which then dimerizes and activates a transcriptional response. Here, we demonstrate that oligomerization-dependent depolarization of excitation light by fused mNeonGreen fluorescent protein probes enables real-time monitoring of RR dimerization dynamics in live bacteria.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!