Ross, J. F. | bioRxiv Science

bioRxiv2024

Structurally diverse calloses/β-1,3-glucans in plant cell wall microdomains

Cell walls underpin the mechanics of cell growth, intercellular signalling, and defence against pathogenic organisms. {beta}-(1,3)-glucans (also known as callose) are polysaccharides found in plants, fungi, and some bacterial species. In developing plant organs, callose accumulates around intercellular channels (plasmodesmata) controlling cell-to-cell communication. We developed monoclonal antibodies for the detection of {beta}-(1,3)-glucans and using these identified distinct populations of callose differing in size and secondary structure. Callose sub-populations were in proximal but not overlapping cell wall microdomains implying distinct spatial and functional microenvironments. We also unveiled callose interaction with xyloglucan; another plant glycan regulating cell wall functions. This work challenges previous views demonstrating structural heterogeneity in plant callose and supporting interactions between glycans with roles in the regulation of cell wall properties and functions.

plant biology↗

bioRxiv2020

De Novo Designed Peptide and Protein Hairpins that Self-assemble into Sheets and Nanoparticles.

The design and assembly of peptide based materials has advanced considerably, leading to a variety of fibrous, sheet and nanoparticle structures. A remaining challenge is to account for and control different possible supramolecular outcomes accessible to the same or similar peptide building blocks. Here we present a de novo peptide system that forms nanoparticles or sheets depending on the strategic placement of a disulfide pin between two elements of secondary structure that drive self-assembly. Specifically, we join homodimerizing and homotrimerizing de novo coiled-coil -helices with a flexible linker to generate a series of linear peptides. The helices are pinned back-to-back, constraining them as hairpins by a disulfide bond placed either proximal or distal to the linker. Computational modeling and advanced microscopy show that the proximally pinned hairpins self-assemble into nanoparticles, whereas the distally pinned constructs form sheets. These peptides can be made synthetically or recombinantly to allow both chemical modifications and the introduction of whole protein cargoes as required.

synthetic biology↗