Publications by Kai Johnsson | EPFL Graph Search

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This paper reports the synthesis of rationally designed polypeptides that catalyze the decarboxylation of oxaloacetate via an imine intermediate. The authors det. the secondary structures of the polypeptides by two-dimensional NMR spectroscopy. The authors are able to trap and identify intermediates in the catalytic cycle, and to explore the kinetics in detail. The formation of the imine by the authors' artificial oxaloacetate decarboxylases is three to four orders of magnitude faster than can be achieved w

We introduce a general method to transform antibodies into ratiometric, bioluminescent sensor proteins for the no-wash quantification of analytes. Our approach is based on the genetic fusion of antibody fragments to NanoLuc luciferase and SNAP-tag, the lat ...

A new strategy for the prepn. of protein-functionalized polymer brushes is reported, which is based on a combination of surface-initiated atom transfer radical polymn. (ATRP), p-nitrophenyl chloroformate activation of the surface hydroxyl groups, and subse ...

SNAP-tag is a powerful tool for labeling proteins with synthetic fluorophores in bioimaging. However, its utility in live-cell applications can be constrained by its relatively slow labeling kinetics and the limited cell permeability of its substrates. Her ...

We introduce a high-affinity split-HaloTag comprised of a short peptide tag (Hpep, 14 residues) and a large, inactive fragment (cpHaloΔ3). Hpep binds to cpHaloΔ3 spontaneously with nanomolar affinity, enabling subsequent labeling with fluorescent HaloTag ligands. The small size of Hpep facilitates cloning-free endogenous protein tagging using CRISPR/Cas9 and the complementation of Hpep-tagged proteins can be achieved in live cells through co-expression with cpHaloΔ3 and in fixed cells through incubation wit

Understanding and controlling the interactions between synthetic and biol. materials is of great importance for the development of novel materials for a variety of biomedical and bioanal. applications, including for example stents, vascular grafts and prot ...

The insertion of peptide loops into the polypeptide chain of proteins at surface-exposed regions is an attractive avenue to modify the protein's properties or to evolve new functionalities. The strategy of peptide loop insertion has, for example, been used to create new binding sites in protein scaffolds and has led to the isolation of proteins with excellent binding affinities for various biological structures. Peptide loops have also been inserted into enzymes to modulate their catalytic properties. We re

The centrosome functions as the main microtubule-organizing center of animal cells and is crucial for several fundamental cellular processes [1]. Abnormalities in centrosome number and composition correlate with tumor progression [2, 3] and other diseases ...

Progress in understanding signal transduction and metabolic pathways is hampered by a shortage of suitable sensors for tracking metabolites, second messengers, and neurotransmitters in living cells. Here we introduce a class of rationally designed semisynt ...

We show that the equilibrium of intramolecular spirocyclization of coumarin-hemicyanine hybrid fluorophores can be finely tuned by means of chemical modifications. We used this scaffold to develop activatable fluorescent probes with large Stokes shifts for ...

We present Rho-tag and SiR-tag, engineered protein tags derived from bacterial multidrug-resistance proteins that bind unsubstituted (silicon-) rhodamines with nanomolar affinity, enabling fast, reversible, and fluorogenic protein labeling. In live cells, Rho-tag labeling occurs within seconds — faster than HaloTag7 — and the tags are compatible with super-resolution methods like STED, SMLM, and MINFLUX. The high specificity of Rho-tag and SiR-tag for unsubstituted rhodamines allows their use alongside Halo

A review of recent developments in the labeling of fusion proteins with synthetic mols. in the living cell or in complex mixts. The most commonly used tags are presented and then focuses on a new class of tags that are not limited to their genetically encoded function but rather serves as general acceptors for synthetic mols. The tetracysteine tag, which reversibly binds to biarsenical compds., and the human O6-alkylguanine-DNA alkyltransferase tag, which is irreversibly alkylated by benzylguanine derivs.,

The ideal fluorescent probe for bioimaging is bright, absorbs at long wavelengths and can be implemented flexibly in living cells and in vivo. However, the design of synthetic fluorophores that combine all of these properties has proved to be extremely difficult. Here, we introduce a biocompatible near-infrared silicon-rhodamine probe that can be coupled specifically to proteins using different labelling techniques. Importantly, its high permeability and fluorogenic character permit the imaging of proteins

Fusion proteins of human O6-alkylguanine-DNA alkyltransferase (AGT) can be specifically labeled with a wide variety of synthetic probes in mammalian cells; this makes them an attractive tool for studying protein function. However, to avoid undesired labeli ...

A method using O-alkylguanine-DNA alkyltransferases (AGT) is disclosed for transferring a label from a substrate to a fusion protein comprising the AGT. This allows the detection and/or manipulating of the fusion protein, both in vitro and in vivo, by attaching molecules to the fusion proteins that introduce a new physical or chemical property to the fusion protein. Examples of such molecules are, among others, spectroscopic probes or reporter molecules, affinity tags, molecules generating reactive radic

The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT, alkyltransferase) is an important suicide enzyme involved in defense against O6-alkylating endogenous metabolites and environmental carcinogens. It also plays a pivotal role in primary and acquired resistance of tumors to alkylating anticancer drugs targeting the O6-position of guanine (i.e., methylating and chloroethylating agents). MGMT can thus be considered a crucial biomarker for individual susceptibility to alkylating carcinogens and

At its most fundamental level, touch sensation requires the translation of mechanical energy into mechanosensitive ion channel opening, thereby generating electro-chemical signals. Our understanding of this process, especially how the cytoskeleton influenc ...

This work is devoted to an "old" defect and its annealing characteristics, namely the divacancy center in Si. IR spectroscopy is applied to study the annealing kinetics of divacancy-related absorption peaks in electron-irradiated Czochralski-grown samples doped with B. In all specimens the kinetics show an exponential decay (first-order process) and a model taking into account both diffusion and dissocn. as annihilation mechanisms gives excellent quant. agreement with the exptl. results. Activation energy

The self-labeling protein tags (SLPs) HaloTag7, SNAP-tag, and CLIP-tag allow the covalent labeling of fusion proteins with synthetic molecules for applications in bioimaging and biotechnology. To guide the selection of an SLP-substrate pair and provide gui ...

A review. The interplay between carbohydrates, lipids, and proteins dets. the stability and flexibility as well as the adhesive and responsive features of the surfaces of all cells. The mol. understanding of the interactions among and between the different ...

Kai Johnsson

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Synthesis, structure and activity of artificial, rationally designed catalytic polypeptides

Bioluminescent Antibodies for Point-of-Care Diagnostics

Protein-Functionalized Polymer Brushes

SNAP-tag2 for faster and brighter protein labeling

A high-affinity split-HaloTag for live-cell protein labeling

Protein-functionalized polymer brushes

Using peptide loop insertion mutagenesis for the evolution of proteins

Selective Chemical Crosslinking Reveals a Cep57-Cep63-Cep152 Centrosomal Complex

Semisynthesis of fluorescent metabolite sensors on cell surfaces

Activatable fluorescent probes for hydrolase enzymes based on coumarin-hemicyanine hybrid fluorophores with large Stokes shifts

Fast, Bright and Reversible Rhodamine Tags for Live-Cell Imaging

A fusion of disciplines: Chemical approaches to exploit fusion proteins for functional genomics

A near-infrared fluorophore for live-cell super-resolution microscopy of cellular proteins

Engineering substrate specificity of O6-alkylguanine-DNA alkyltransferase for specific protein labeling in living cells

Methods using o-alkylguanine-dna alkyltransferases

DNA repair protein O6-methylguanine-DNA methyltransferase in testis and testicular tumors as determined by a novel nonradioactive assay

Acetylated tubulin is essential for touch sensation in mice

Annealing of divacancy-related infrared absorption bands in boron-doped silicon

Kinetic and Structural Characterization of the Self-Labeling Protein Tags HaloTag7, SNAP-tag, and CLIP-tag

Protein chemistry on the surface of living cells