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Kai Johnsson

Cette personne a quitté l’EPFL

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Publications associées (122)

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Investigating Endocytic Pathways to the Endoplasmic Reticulum and to the Cytosol Using SNAP-Trap

Kai Johnsson

Cholera toxin enters cells via an unusual pathway that involves trafficking through endosomes to the endoplasmic reticulum (ER). Whether the toxin induces its own pathway or travels along a physiological retrograde route is not known. To study its traffick ...

Wiley-Blackwell2013

Sensing Acetylcholine and Anticholinesterase Compounds

Kai Johnsson, Alberto Schena

Acetylcholine is a key neurotransmitter, and anticholinesterase agents are essential compounds used as medical drugs, pesticides, and chemical warfare agents. A semisynthetic fluorescence-based probe for the direct, real-time detection of acetylcholine and ...

Wiley-Blackwell2013

Semisynthetic sensor proteins enable metabolic assays at the point of care

Kai Johnsson, Rudolf Griss, Qiuliyang Yu, Lin Xue, Julien Hiblot

Monitoring metabolites at the point of care could improve the diagnosis and management of numerous diseases. Yet for most metabolites, such assays are not available. We introduce semisynthetic, light-emitting sensor proteins for use in paper-based metaboli ...

American Association for the Advancement of Science2018

Expression proteomics study to determine metallodrug targets and optimal drug combinations

Paul Joseph Dyson, Kai Johnsson, David Hacker, Claire Samantha Allardyce

The emerging technique termed functional identification of target by expression proteomics (FITExP) has been shown to identify the key protein targets of anti-cancer drugs. Here, we use this approach to elucidate the proteins involved in the mechanism of a ...

Nature Research2017

Compositions and use of sulfasalazine

Kai Johnsson, Christopher Chidley

The invention relates to compositions comprising sulfasalazine or sulfapyridine and products of a biosynthetic pathway that requires tetrahydrobiopterin. Such compositions are useful for the treatment of inflammatory bowel diseases or rheumatoid arthritis, ...

2011

Chemical Genetic Screen Identifies Natural Products that Modulate Centriole Number

Zhou Fang, Michele Graciotti, Pierre Gönczy, Kai Johnsson

Centrioles are microtubule-based organelles found in most eukaryotic cells and that are critical for the formation of cilia and flagella, as well as of centrosomes in animal cells. The number of centrioles must be strictly regulated in proliferating cells ...

Wiley-Blackwell2016

Computational design of environmental sensors for the potent opioid fentanyl

Kai Johnsson, Luc Reymond

We describe the computational design of proteins that bind the potent analgesic fentanyl. Our approach employs a fast docking algorithm to find shape complementary ligand placement in protein scaffolds, followed by design of the surrounding residues to opt ...

Elife Sciences Publications Ltd2017

Molecular recording of cellular protein kinase activity with chemical labeling

Kai Johnsson

Protein kinases control most cellular processes and aberrant kinase activity is involved in numerous diseases. Here we introduce molecular recorders of kinase activities for later analysis to investigate the link between specific kinase activities and cell ...

2025

Visualizing Biochemical Activities in Living Cells through Chemistry

Kai Johnsson, Luc Reymond, Rudolf Griss, Alberto Schena, Grazvydas Lukinavicius, Matthias Albert Brun, Karolina Bojkowska, Birgit Mollwitz, Anastasiya Masharina

The development of molecular probes to visualize cellular processes is an important challenge in chemical biology. One possibility to create such cellular indicators is based on the selective labeling of proteins with synthetic probes in living cells. Over ...

2011

Targeted Photoswitchable Probe for Nanoscopy of Biological Structures

Theo Lasser, Kai Johnsson, Iwan Märki, Claudio Dellagiacoma, Stefan Geissbühler, Noelia Laura Bocchio, Grazvydas Lukinavicius, Sambashiva Banala

We introduce a photoswitchable O6-benzylguanine derivative and demonstrate its use for super-resolution microscopy of SNAP-tagged proteins based on single fluorophore localization. Stochastic Optical Reconstruction Microscopy (STORM) reveals SNAP-tagged mi ...

2010

Triplet imaging of oxygen consumption during the contraction of a single smooth muscle cell (A7r5)

Dimitri Nestor Alice Van De Ville, Theo Lasser, Kai Johnsson, Marcel Leutenegger, Iwan Märki, Boris Hinz, Aurélie Formey de Saint Louvent, Thiemo Spielmann, Matthias Geissbühler

Triplet imaging is a novel optical technique that allows investigating oxy- gen metabolism at the single cell and the sub-cellular level. The method combines high temporal and spatial resolution, which are required for the monitoring of fast kinetics of ox ...

Springer Science+Business Media2012

Synergizing Exchangeable Fluorophore Labels for Multitarget STED Microscopy

Kai Johnsson

Investigating the interplay of cellular proteins with optical microscopy requires multitarget labeling. Spectral multiplexing using high-affinity or covalent labels is limited in the number of fluorophores that can be discriminated in a single imaging expe ...

AMER CHEMICAL SOC2022

A biosensor for measuring NAD(+) levels at the point of care

Johan Auwerx, Kai Johnsson, Luc Patiny, Elena Katsyuba, Lin Xue, Qiuliyang Yu

The cellular level of nicotinamide adenine dinucleotide (NAD(+)), through its different functions, affects cellular metabolism and signalling(1-3). A decrease in the NAD(+) content has been associated with various pathologies and physiological aging(4,5), ...

NATURE PUBLISHING GROUP2019

Directed evolution of the suicide protein O⁶-alkylguanine-DNA alkyltransferase for increased reactivity results in an alkylated protein with exceptional stability

Ursula Röthlisberger, Kai Johnsson, Florence Pojer, Elizabeth Claire Brunk, Birgit Mollwitz, Simone Schmitt

Here we present a biophysical, structural, and computational analysis of the directed evolution of the human DNA repair protein O-6-alkylguanine-DNA alkyltransferase (hAGT) into SNAP-tag, a self-labeling protein tag. Evolution of hAGT led not only to incre ...

2012

Yeast Three-Hybrid Screening for Identifying Anti-Tuberculosis Drug Targets

Kai Johnsson, Simone Moser

Mycobacterium goes yeast: Target deconvolution of anti-tuberculosis drugs can be a very challenging task. Here we report a yeast 3-hybrid system that allows promising small molecules to be screened for protein targets of a pathogen in nontoxic yeast cells. ...

Wiley-V C H Verlag Gmbh2013

Adding value to fusion proteins through covalent labeling

Kai Johnsson, Thomas Gronemeyer

A review. Recombinant proteins are often expressed with an addnl. polypeptide the role of which is to aid purifn., detection, or functional studies. Recently, the role of these tags has been extended to mediate the labeling of the protein of interest with ...

2005

Mutants of o6-alkylguanine-dna alkyltransferase

Kai Johnsson, Christian Heinis, Christopher Chidley, Alexandre Juillerat, Antje Keppler, Thomas Gronemeyer

The invention relates to AGT mutants showing, when compared to the wild type human AGT, two or more advantageous properties selected from (a) reduced DNA interaction (b) localisation of the expressed protein in eukaryotic cells that is no longer restricted ...

2006

Environmentally Sensitive Color-Shifting Fluorophores for Bioimaging

Kai Johnsson, Julien Hiblot

We introduce color-shifting fluorophores that reversibly switch between a green and red fluorescent form through intramolecular spirocyclization. The equilibrium of the spirocyclization is environmentally sensitive and can be directly measured by determini ...

Wiley-VCH Verlag GmbH2020

A synergistic strategy to develop photostable and bright dyes with long Stokes shift for nanoscopy

Kai Johnsson

The quality and application of super-resolution fluorescence imaging greatly lie in the dyes' properties, including photostability, brightness, and Stokes shift. Here we report a synergistic strategy to simultaneously improve such properties of regular flu ...

Nature Portfolio2022

Sensor molecules and uses thereof

Kai Johnsson, Rudolf Griss, Alberto Schena

The invention generally relates to methods, reagents and devices for determining a concentration of an analyte in a sample. Provided is a proteinaceous sensor molecule for detecting an analyte of interest (A), comprising a signal generating moiety tethered ...

2015