Niklaus Johner

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Active exchangers dissipate the gradient of one substrate to accumulate nutrients, export xenobiotics and maintain cellular homeostasis. Mechanistic studies have suggested that two fundamental properties are shared by all exchangers: substrate binding is antagonistic, and coupling is maintained by preventing shuttling of the empty transporter. The CLC(More)
We present an in-depth analysis of the geometrical percolation behavior in the continuum of random assemblies of hard oblate ellipsoids of revolution. Simulations were carried out by considering a broad range of aspect ratios, from spheres up to aspect-ratio-100 platelike objects, and with various limiting two-particle interaction distances, from 0.05 times(More)
Recent successes in the crystallographic determination of structures of transmembrane proteins in the G protein-coupled receptor (GPCR) family have established the lipidic cubic phase (LCP) environment as the medium of choice for growing structure-grade crystals by the method termed "in meso". The understanding of in meso crystallogenesis is currently at a(More)
Experimental observations of the dependence of function and organization of G protein-coupled receptors (GPCRs) on their lipid environment have stimulated new quantitative studies of the coupling between the proteins and the membrane. It is important to develop such a quantitative understanding at the molecular level because the effects of the coupling are(More)
Research projects in structural biology increasingly rely on combinations of heterogeneous sources of information, e.g. evolutionary information from multiple sequence alignments, experimental evidence in the form of density maps and proximity constraints from proteomics experiments. The OpenStructure software framework, which allows the seamless(More)
The recent advances in the in meso crystallization technique for the structural characterization of G-protein coupled receptor (GPCR) proteins have established the usefulness of the lipidic-cubic phases (LCPs) in the field of crystallography of membrane proteins. It is surprising that despite the success of the approach, the molecular mechanisms of the in(More)
We examine the effects of cholesterol (Chol) on the mechanical properties of membranes consisting of 16:0/18:1 POPC lipid and of lipids with conjugated linoleic acid (CLA), cis-9/trans-11 CLA (C9T11) and trans-10/cis-12 CLA (T10C12). Atomistic molecular dynamics (MD) simulations of POPC-Chol and CLA-Chol mixtures at various Chol concentrations are employed(More)
PICK1 is a neuronal scaffolding protein containing a PDZ domain and an auto-inhibited BAR domain. BAR domains are membrane-sculpting protein modules generating membrane curvature and promoting membrane fission. Previous data suggest that BAR domains are organized in lattice-like arrangements when stabilizing membranes but little is known about structural(More)
We evaluate the percolation threshold values for a realistic model of continuum segregated systems, where random spherical inclusions forbid the percolating objects, modeled by hardcore spherical particles surrounded by penetrable shells, to occupy large regions inside the composite. We find that the percolation threshold is generally a nonmonotonous(More)
The dopamine transporter (DAT) is a transmembrane protein belonging to the family of neurotransmitter:sodium symporters (NSS). Members of the NSS are responsible for the clearance of neurotransmitters from the synaptic cleft, and for their translocation back into the presynaptic nerve terminal. The DAT contains long intracellular N- and C-terminal domains(More)