Biology subjects

Autzen, A. A. A.

Publications and source records attributed to Autzen, A. A. A..

4 recordsLinked to original sources

bioRxiv2024

MAASTY: A (dis)ordered copolymer for structural determination of human membrane proteins in native nanodiscs

Amphiphilic copolymers capable of extracting membrane proteins directly from cellular membranes into "native nanodiscs" offer a simplified approach for preparing membrane proteins in lipid nanodiscs compared to approaches that rely on detergent. Amphiphilicity, length, and composition influence the performance of copolymers, in addition to the protein itself and the purification conditions used. Here, we report a copolymer composed of methacrylic acid and styrene, which we term MAASTY, leveraging the inherent monomer reactivity ratios to create an anionic copolymer with a statistical distribution of monomers. We show that MAASTY can be used for high-resolution structural determination of a human membrane protein with single particle cryo-electron microscopy, preserving endogenous lipids including cholesterol and exhibiting an enrichment of phosphatidylinositol. Moreover, MAASTY copolymers effectively solubilize a broad range of lipid species and a wide range of different, eukaryotic membrane proteins from mammalian cells. We find that MAASTY copolymers are promising as effective solubilizers of membrane proteins and offer a chemical platform for structural and functional characterization of membrane proteins in native nanodiscs.

biochemistry↗

bioRxiv2023

Functionalized graphene-oxide grids enable high-resolution cryo-EM structures of the SNF2h-nucleosome complex without crosslinking

Single-particle cryo-EM is widely used to determine enzyme-nucleosome complex structures. However, cryo-EM sample preparation remains challenging and inconsistent due to complex denaturation at the air-water interface (AWI). To address this issue, we developed graphene-oxide-coated EM grids functionalized with either single-stranded DNA (ssDNA) or thiol-poly(acrylic acid-co-styrene) (TAASTY) co-polymer. These grids protect complexes between the chromatin remodeler SNF2h and nucleosomes from the AWI and facilitated collection of high-quality micrographs of intact SNF2h-nucleosome complexes in the absence of crosslinking. The data yields maps ranging from 2.3 to 3 [A] in resolution. 3D variability analysis reveals nucleotide-state linked conformational changes in SNF2h bound to a nucleosome. In addition, the analysis provides structural evidence for asymmetric coordination between two SNF2h protomers acting on the same nucleosome. We envision these grids will enable similar detailed structural analyses for other enzyme-nucleosome complexes and possibly other protein-nucleic acid complexes in general.

biochemistry↗

bioRxiv2023

Cancer Immunotherapy through Tissue Adhering Polymers

TLR 7/8 agonists are highly potent immunostimulators, though their clinical translation has been met with mixed success, due to their high toxicity as a result of an unregulated systemic immune activation. There is enormous potential to augment cancer immunotherapies with synthetic TLR 7/8 agonists, though a thorough control of pharmacokinetics and localization is needed for the general use of TLR 7/8 agonists in cancer immunotherapy. Herein, we control localization of TLR 7/8 agonists, by exploiting the extensive tissue retention of poly(acrylic acid-co-styrene). In a murine CT26 model, we find that covalently attaching TLR 7/8 agonists to the copolymer allows for retaining the drug in the tumor microenvironment for at least 15 weeks, after intratumoral injection, and results in a curative monotherapy. The copolymer itself is a new avenue for attaining prolonged tissue rentention for covalently attached drugs.

cancer biology↗

bioRxiv2021

Characterization of divalent cation interactions with AASTY nanodiscs

Amphiphilic copolymers show promise in extracting membrane proteins directly from lipid bilayers into native nanodiscs. However, many such copolymers are polyanionic and sensitive to divalent cations, limiting their applicability. We characterize the Ca2+ and Mg2+ sensitivity of poly(acrylic acid-co-styrene) (AASTY) copolymers with analytical UV and fluorescent size exclusion chromatography, enabling us to separate signals from nanodiscs, copolymers, and soluble aggregates. We find that divalent cations promote aggregation and precipitation of both free and lipid bound copolymers. We see that excess, free copolymer acts as a cation sink that protects nanodiscs from Ca2+ induced aggregation. Removal of the free copolymer through dialysis induces aggregation that can be mitigated by KCl. Finally, we find that the nanodisc size is dynamic and dependent on lipid concentration. Our results offer insight to nanodisc behaviour, and can help guide experimental design, aimed at mitigating the shortcomings inherent in negatively charged nanodisc forming copolymers.

biochemistry↗