Biology subjects

Spichty, M.

Publications and source records attributed to Spichty, M..

7 recordsLinked to original sources

bioRxiv2024

Accurate interaction between silver(I) ion and amino acid side chains with the 12-6 Lennard-Jones potential: a bottom-up parameterization approach

Silver(I) ions and organometallic complexes thereof are well established antimicrobial agents. They have been employed in medical applications for centuries. It is also known that some bacteria can resist to silver(I) treatments through an efflux mechanism. However, the exact mechanism of action remains unclear. All-atom force-field simulations can provide valuable structural and thermodynamic insights on the molecular processes of the underlying mechanism. Lennard-Jones parameters of silver(I) have been available for quite some time; their applicability to describe properly the binding properties (affinity, binding distance) between silver(I) and peptide-based binding motifs is, however, still an open question. Here, we demonstrate that the standard 12-6 Lennard-Jones parameters (previously developed to describe the hydration free energy with the TIP3P water model) significantly underestimate the interaction strength between silver(I) and both methionine and histidine. These are two key amino-acid residues in silver(I)-binding motifs of proteins involved in the efflux process. Using free-energy calculations, we calibrated non-bonded fix (NBFIX) parameters for the CHARMM36m force field to reproduce the experimental binding constant between amino acid sidechain fragments and silver(I) ions. We then successfully validated the new parameters on a set of small silver-binding peptides with experimentally known binding constants. In addition, we could monitor how silver(I) ions increase the -helical content of the LP1 oligopeptide, in agreement with previously reported Circular Dichroism (CD) experiments. Future improvements are outlined. The implementation of these new parameters is straightforward in all simulation packages that can use the CHARMM36m force field. It sets the stage for the modeling community to study more complex silver(I)-binding processes such as the interaction with silver(I)-binding-transporter proteins.

biophysics↗

bioRxiv2023

Dissecting Key Multivalent Processes in Glycosidase Inhibition: Insights from Thermodynamic Modelling and Atomistic Simulations

Multivalency represents a powerful approach to increase the inhibition potency of moderate glycosidase inhibitors. Regarding the key role of catalytic glycoside hydrolysis in biology, understanding the molecular mechanisms and origin of the multivalent inhibitory effect is of great interest and presents a fascinating playground for theoretical studies. Our teams have recently dissected key processes of multivalent glycosidase inhibition through the use of different neoglycoclusters based on deoxynojirimycin (DNJ) inhitopes and a cyclopeptoid scaffold. This companion article details the theoretical aspects of this former study. A thermodynamic model is developed and validated, compared to literature, and extended to account for particularities of the charged DNJ inhitopes.

biochemistry↗

bioRxiv2020

A monogenic and fast-responding Light-Inducible Cre recombinase as a novel optogenetic switch

ABSTRACTOptogenetics enables genome manipulations with high spatiotemporal resolution, opening exciting possibilities for fundamental and applied biological research. Here, we report the development of LiCre, a novel light-inducible Cre recombinase. LiCre is made of a single flavin-containing protein comprising the asLOV2 photoreceptor domain of Avena sativa fused to a Cre variant carrying destabilizing mutations in its N-terminal and C-terminal domains. LiCre can be activated within minutes of illumination with blue light, without the need of additional chemicals. When compared to existing photoactivatable Cre recombinases based on two split units, LiCre displayed faster and stronger activation by light as well as a lower residual activity in the dark. LiCre was efficient both in yeast, where it allowed us to control the production of β-carotene with light, and in human cells. Given its simplicity and performances, LiCre is particularly suited for fundamental and biomedical research, as well as for controlling industrial bioprocesses.Competing Interest StatementThe authors declare the following competing interest: A patent application covering LiCre and its potential applications has been filed. Patent applicant: CNRS; inventors: Helene Duplus-Bottin, Martin Spichty and Gael Yvert.View Full Text

synthetic biology↗

bioRxiv2020

Titration of in-cellula affinities of protein-protein interactions

A genetic assay permits simultaneous quantification of two interacting proteins and their bound fraction at the single-cell level using flow cytometry. In-cellula affinities of protein-protein interactions can be extracted from the acquired data through a titration-like analysis. The applicability of this approach is demonstrated on a diverse set of interactions with proteins from different families and organisms and with in-vitro dissociation constants ranging from picomolar to micromolar.

biochemistry↗

bioRxiv2019

A quantitative tri-fluorescent yeast two-hybrid system: from flow cytometry to in-cellula affinities

We present a technological advancement for the estimation of the affinities of Protein-Protein Interactions (PPIs) in living cells. A novel set of vectors is introduced that enables a quantitative yeast two-hybrid system based on fluorescent fusion proteins. The vectors allow simultaneous quantification of the reaction partners (Bait and Prey) and the reporter at the single-cell level by flow cytometry. We validate the applicability of this system on PPIs with different affinities. After only two hours of reaction, expression of the reporter can easily be detected even for the weakest PPI. Through a simple gating analysis, it is possible to select only cells with identical expression levels of the reaction partners. As a result of this standardization of expression levels, the mean reporter levels directly reflects the affinities of the studied PPIs. With a set of PPIs with known affinities, it is straightforward to construct an affinity ladder that permits rapid classification of PPIs with thus far unknown affinities. Conventional software can be used for this analysis. To permit automated high-throughput analysis, we provide a graphical user interface for the Python-based FlowCytometryTools package.

biochemistry↗

bioRxiv2018

Physical and functional interaction between SET1/COMPASS complex component CFP-1 and a Sin3 HDAC complex

The CFP1 CXXC zinc finger protein targets the SET1/COMPASS complex to non-methylated CpG rich promoters to implement tri-methylation of histone H3 Ly4 (H3K4me3). Although H3K4me3 is widely associated with gene expression, the effects of CFP1 loss depend on chromatin context, so it is important to understand the relationship between CFP1 and other chromatin factors. Using a proteomics approach, we identified an unexpected link between C. elegans CFP-1 and a Rpd3/Sin3 histone deacetylase complex. We find that mutants of CFP-1, SIN-3, and the catalytic subunit SET-2/SET1 have similar phenotypes and misregulate common genes. CFP-1 directly binds SIN-3 through a region including the conserved PAH1 domain and recruits SIN-3 and the HDA-1/HDAC subunit to H3K4me3 enriched promoters. Our results reveal a novel role for CFP-1 in mediating interaction between SET1/COMPASS and a Sin3 HDAC complex at promoters and uncover coordinate regulation of gene expression by chromatin complexes having distinct activities.

genomics↗

bioRxiv2017

Assigning Function To Natural Allelic Variation Via Dynamic Modeling Of Gene Network Induction

More and more natural DNA variants are being linked to physiological traits. Yet, understanding what differences they make on molecular regulations remains challenging. Important properties of gene regulatory networks can be captured by computational models. If model parameters can be personalized according to the genotype, their variation may then reveal how DNA variants operate in the network. Here, we combined experiments and computations to visualize natural alleles of the yeast GAL3 gene in a space of model parameters describing the galactose response network. Alleles altering the activation of Gal3p by galactose were discriminated from those affecting its activity (production/degradation or efficiency of the activated protein). The approach allowed us to correctly predict that a non-synonymous SNP would change the binding affinity of Gal3p with the Gal80p transcriptional repressor. Our results illustrate how personalizing gene regulatory models can be used for the mechanistic interpretation of genetic variants.

systems biology↗