Biology subjects

Baumann, C.

Publications and source records attributed to Baumann, C..

5 recordsLinked to original sources

bioRxiv2026

Transmembrane domain composition reflects subcellular localization of SNARE proteins

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=128 SRC="FIGDIR/small/713902v1_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@1800a38org.highwire.dtl.DTLVardef@11f19aborg.highwire.dtl.DTLVardef@ce3b90org.highwire.dtl.DTLVardef@1a8935b_HPS_FORMAT_FIGEXP M_FIG C_FIG Transmembrane domains (TMDs) anchor proteins within membranes of distinct composition and biophysical properties, necessitating adaptation to each membranes unique environment. SNARE proteins, the core mediators of eukaryotic membrane fusion, provide an ideal system to study such adaptations: they are ubiquitous across Eukaryota, with paralogs localized to different compartments that have evolved independently to match their membrane context. Here, we combine statistical analyses of approximately 14,000 SNARE TMDs with MD simulations of 28 human SNARE TMDs to uncover how TMDs have adapted to distinct membrane environments. We identify a clear compositional dichotomy that separates SNAREs of the early secretory pathway (ER and Golgi apparatus) from those of the late secretory and endosomal pathways: early TMDs are enriched in bulky Phe residues, whereas late TMDs are dominated by smaller Ile residues. The larger Phe side chains likely enhance hydrophobic interactions in loosely packed ER and Golgi membranes, while Ile likely prevents disruption of the tight lipid-lipid packing in the plasma and endosomal membranes, thereby contributing to protein localization. TMD lengths derived from MD simulations differ from those inferred by sequence-based approaches and show limited variations across compartments. Together, these results reveal how variations in membrane composition shaped SNARE TMDs across eukaryotic compartments.

molecular biology↗

bioRxiv2025

Simultaneous measurements of translation rate and transcriptome in single bacterial cells by scTR-seq uncovers linked regulation within a specialized active cell population.

Cell-to-cell variation within clonal bacterial populations provides bacterial communities important advantages including opportunities for bet-hedging and metabolic division of labor. In recent years the extent of bacterial heterogeneity has been documented both at the transcriptome level and with physiological measurements of cell growth rate and translation rate. However, methods that link physiological parameters to a single cells full transcriptomic state are lacking, making it difficult to identify the regulatory mechanisms that couple physiology and transcriptional output. Here we introduce a method that combines click-chemistry enabled labeling of nascent polypeptides to measure translation rates in single cells alongside microfluidic encapsulation and single cell transcriptomic measurements, providing a tandem measurement of translation rate and transcriptome in thousands of single Bacillus subtilis cells. In a culture experiencing nutrient limitation, we identified a subpopulation of cells with a higher rate of protein translation that uniquely overexpresses genes for several metabolic processes including acetoin production and arginine synthesis. Using a genetic approach informed by the gene expression in this subpopulation, we identified a regulatory mechanism that couples the increase in protein abundance of a transcriptional regulator AlsR with expression of alsR regulated genes in this subpopulation.

microbiology↗

bioRxiv2024

PEARL: Protein Eluting Alginate with Recombinant Lactobacilli

Engineered living materials (ELMs) made of bacteria in hydrogels have shown considerable promise for therapeutic applications through controlled and sustained release of complex biopharmaceuticals at low costs and with reduced wastage. While most therapeutic ELMs use E. coli due to its large genetic toolbox, most live biotherapeutic bacteria in development are lactic acid bacteria due to native health benefits they offer. Among these, lactobacilli form the largest family of probiotics with therapeutic potential in almost all sites of the body with a microbiome. A major factor limiting the use of lactobacilli in ELMs is their limited genetic toolbox. In this study, we build upon our recent work to expand the genetic programmability of probiotic Lactiplantibacillus plantarum WCFS1 for protein secretion and encapsulate it in a simple, cost-effective, and biocompatible core-shell alginate bead to develop an ELM. We demonstrate the controlled release of recombinant proteins, even up to 14 days from this ELM, thereby terming it PEARL - Protein Eluting Alginate with Recombinant Lactobacilli. Notably, lactobacillus encapsulation offered benefits like bacterial containment, protein release profile stabilization, and metabolite-induced cytotoxicity prevention. These findings demonstrate the mutual benefits of combining recombinant lactobacilli with alginate for the controlled and sustained release of proteins.

bioengineering↗

bioRxiv2023

Side-Chain Dynamics of the α1B-Adrenergic Receptor determined by NMR via Methyl Relaxation

G protein-coupled receptors (GPCRs) are medically important membrane proteins that sample inactive, intermediate, and active conformational states characterized by relatively slow interconversions ([~]s- ms). On a faster timescale ([~]ps-ns), the conformational landscape of GPCRs is governed by the rapid dynamics of amino acid side chains. Such dynamics are essential for protein functions such as ligand recognition and allostery. Unfortunately, technical challenges have almost entirely precluded the study of side-chain dynamics for GPCRs. Here, we investigate the rapid side-chain dynamics of a thermostabilized 1B-adrenergic receptor (1B-AR) as probed by methyl relaxation. We determined order parameters for Ile, Leu, and Val methyl groups in the presence of inverse agonists that bind orthosterically (prazosin, tamsulosin) or allosterically (conopeptide {rho}-TIA). Despite the differences in the ligands, the receptors overall side-chain dynamics are very similar, including those of the apo form. However, {rho}-TIA increases the flexibility of Ile1764x56 and possibly of Ile2145x49, adjacent to Pro2155x50 of the highly conserved P5x50I3x40F6x44 motif crucial for receptor activation, suggesting differences in the mechanisms for orthosteric and allosteric receptor inactivation. Overall, increased Ile side-chain rigidity was found for residues closer to the center of the membrane bilayer, correlating with denser packing and lower protein surface exposure. In contrast to two microbial membrane proteins, in 1B-AR Leu exhibited higher flexibility than Ile side chains on average, correlating with the presence of Leu in less densely packed areas and with higher protein-surface exposure than Ile. Our findings demonstrate the feasibility of studying receptor-wide side-chain dynamics in GPCRs to gain functional insights.

biophysics↗

bioRxiv2022

Differential UBE2H-CTLH E2-E3 ubiquitylation modules regulate erythroid maturation

The development of haematopoietic stem cells into mature erythrocytes - erythropoiesis - is a controlled process characterized by cellular reorganisation and drastic reshaping of the proteome landscape. Failure of ordered erythropoiesis is associated with anaemias and haematological malignancies. Although the ubiquitin (UB) system is a known crucial post-translational regulator in erythropoiesis, how the erythrocyte is reshaped by the UB system is poorly understood. By measuring the proteomic landscape of in vitro human erythropoiesis models, we found dynamic differential expression of subunits of the CTLH E3 ubiquitin ligase complex that formed distinct maturation stage-dependent assemblies of structurally homologous RANBP9-and RANBP10-CTLH complexes. Moreover, protein abundance of CTLHs cognate E2-conjugating enzyme UBE2H increased during terminal differentiation, which depended on catalytically active CTLH E3 complexes. CRISPR-Cas9 mediated inactivation of all CTLH E3 assemblies by targeting the catalytic subunit MAEA, or UBE2H, triggered spontaneous and accelerated maturation of erythroid progenitor cells including increased heme and haemoglobin synthesis. Thus, the orderly progression of human erythropoiesis is controlled by the assembly of distinct UBE2H-CTLH modules functioning at different developmental stages.

cell biology↗