Biology subjects

Weiss, I. M.

Publications and source records attributed to Weiss, I. M..

4 recordsLinked to original sources

bioRxiv2026

Elucidating the functional domain architecture of ArCS1, a biomineralizing myosin chitin synthase: I. The role of lipids

In molluscs, chitin synthases are essential for biologically controlled biomineralization, with some variants possessing a myosin motor domain that may link polymer synthesis to the cytoskeleton. Experimentally, we established a reliable workflow for expressing ArCS1_E22TM in Dictyostelium discoideum and developed effective purification methods to reconstitute ArCS1_E22TM in nanodiscs using MSPs and specific lipid composition. MSP1D1deltaH5 proved optimal for nanodisc formation, yielding homogeneous, monodisperse discs (~8.2 nm). Lipids were refined to POPC:POPE:POPG (3:1:1) with 20% cholesterol, improving nanodisc quality and uniformity as observed by negative-stain EM. The full-length ArCS1 and its subdomains were modeled using AlphaFold3; the myosin motor, glycosyltransferase, and transmembrane regions are well-defined internally but loosely constrained relative to one another, suggesting flexible linking and conformational coupling. Modelling with Mg2+ and oleic acid as ligands and comparative analyses with bacterial cellulose synthase and yeast chitin synthase 1 provided insights into substrate binding and a potential mechanism for chitin polymerization and translocation. This research establishes a standard procedure for comprehensive structural analyses of recombinant molluscan chitin synthase in near-native or biomimetic membranes. This sets the stage for high-resolution cryo-electron microscopy to determine the first experimentally resolved structure of a molluscan chitin synthase and to provide insight into the enzyme's architecture and the regulatory mechanisms of biomineralization.

molecular biology↗

bioRxiv2026

Synthetic iminosugar monomers change global metabolic pathways and chitin biosynthesis in Thalassiosira rotula

- Thalassiosira rotula produces extracellular chitin fibers of interest for material science. Tailored monomeric iminosugars, designed as substrate analogues for carbohydrate-active enzymes, unexpectedly elongate these fibers in vivo, yet their impact on chitin metabolism remains unclear. - T.rotula was exposed to three L-isoleucine-derived iminosugar analogues immediately before cell division, when chitin fibers are produced. RNA-sequencing, combined with differential expression and pathway enrichment analyses, as well as transcriptome mining for chitin-related genes was performed. - Gene mining identified 84 chitin-associated genes (including 42 chitin synthases). Two iminosugars globally repressed carbohydrate- and energy-related pathways including photosynthesis, glycolysis/gluconeogenesis, and Calvin cycle while simultaneously inducing ribosome biogenesis. ImOH specifically downregulated 29 chitin-related genes, including two strongly repressed chitinases and a {beta}-N-acetylhexosaminidase. - Tailored monomeric chitin-modulating iminosugars not only alter chitin fiber length but also trigger a broad metabolic shift from carbohydrate synthesis toward ribosome biogenesis, indicative of a cellular stress response to non-metabolizable iminosugars.

plant biology↗

bioRxiv2024

Feather keratin in Pavo cristatus: A tentative structure

The filament of the F-keratin polymer is an alternating arrangement of two tetrameric sequence segments, the "N-block" made of four strands AA 1-52, a twisted parallelepiped and the "C-block", a sandwich of four strands AA 81-100. The N-blocks have 89{degrees}internal rotation within eight levels of {beta}-sandwiches strengthened by three disulfide bonds per monomer. The C-blocks contain 5 aromatic residues, they provide resilience, like vertebral discs in a spinal column. The pitch of an N+C-block octamer is 10 nm. Solidification of F-keratin may involve the "C-blocks" to temporarily mold into "C-wedges" of 18{degrees} tilt, which align the polymer filaments into laterally amorphous fiber-reinforced composites of 9.5 nm axial periodicity. This distance corresponds to the length of the fully stretched AA 53-80 matrix segment. The "spinal column" is deformed like in scoliosis and unwinds under compression when F-keratin filaments perfectly align horizontally and form stacked sheets in the solid state.

biophysics↗

bioRxiv2017

Thermal Decomposition Of The Amino Acids Glycine, Cysteine, Aspartic Acid, Asparagine, Glutamic Acid, Glutamine, Arginine And Histidine

Calorimetry, thermogravimetry and mass spectrometry were used to follow the thermal decomposition of the eight amino acids G, C, D, N, E, Q, R and H between 185{degrees}C and 280{degrees}C. Endothermic heats of decomposition between 72 and 151 kJ/mol are needed to form 12 to 70 % volatile products. This process is neither melting nor sublimation. With exception of cysteine they emit mainly H2O, some NH3 and no CO2. Cysteine produces CO2 and little else. The reactions are described by polynomials, AA ^ a (NH3) + b (H2O) + c (CO2) + d (H2S) + e (residue), with integer or half integer coefficients. The solid monomolecular residues are rich in peptide bonds.

biochemistry↗