Biology subjects

Yim, L.

Publications and source records attributed to Yim, L..

3 recordsLinked to original sources

bioRxiv2026

Hierarchical decoding of targeting tripeptide motif by the cytosolic iron-sulfur cluster assembly targeting complex

Iron-sulfur (Fe-S) clusters are essential cofactors required for diverse cellular processes, yet how the Fe-S cluster biogenesis machinery selectively recognizes apo-client proteins remain poorly understood. In eukaryotes, many cytosolic and nuclear Fe-S proteins are recruited to the cytosolic iron-sulfur cluster assembly (CIA) system through a short C-terminal targeting complex recognition (TCR) motif having a [ILM]-[DES]-FW] consensus. Currently, the physicochemical properties underlying this molecular recognition event are undefined. By combining quantitative binding measurements, bioinformatic analysis, and structural modeling, we define the molecular basis for TCR peptide recognition by the CIA targeting complex (CTC). This systematic energetic dissection reveals a hierarchy of binding determinants, in which the side chain and C-terminal carboxylate of the aromatic residue provide the dominant energetic contributor, whereas the upstream residues modulate affinity in a sequence context-dependent manner. Computational docking and molecular dynamics simulations identify an interfacial binding site at the Cia1-Cia2 interface that can accommodate these TCR moieties complementary interaction surfaces. Mutational analysis the identified interaction site is consistent with an aromatic pocket and an adjacent hydrophobic groove on Cia2 accommodating the TCRs terminal aromatic and antepenultimate aliphatic residues. Together, these results reveal the physicochemical decoding grammar by which the CTC recognizes targeting peptides with divergent sequences, illustrating how short targeting motifs can achieve both the specificity and adaptability required for Fe-S protein maturation. Significance StatementIron-sulfur (Fe-S) clusters are essential metallocofactors requiring dedicated pathways for their assembly and insertion into proteins. How Fe-S cluster biogenesis systems selectively recognize their Fe-S binding client proteins in the crowded cellular environment remains poorly understood, in part because these machineries must engage dozens of clients rather than relying on the one-to-one metallochaperone-client pairings commonly used to assemble other types of metalloproteins. In eukaryotes, many cytosolic and nuclear Fe-S proteins are recruited to the cytosolic iron-sulfur assembly (CIA) machinery through a C-terminal targeting tripeptide motif. Here we combine biochemical measurements and structural modeling to define the molecular rules governing recognition of CIA targeting peptides. We show that a hierarchy of physicochemical peptide features, rather than a strict sequence consensus, guides recruitment of clients to the targeting complex, explaining how a single binding site can decode multiple targeting peptide signals.

biochemistry↗

bioRxiv2023

Lung cancer-intrinsic SOX2 expression mediates resistance to checkpoint blockade therapy by inducing Treg-dependent CD8+ T cell exclusion

Tumor-intrinsic signaling pathways can drastically affect the tumor immune microenvironment (TME), promoting tumor progression and resistance to immunotherapy by excluding immune cell populations from the tumor. Several tumor-cell intrinsic pathways have been reported to affect myeloid cell infiltration and downstream T cell infiltration. Clinical evidence suggests that the exclusion of cytotoxic T cells from the tumor core likewise mediates resistance. Here, we find that tumor cell-intrinsic SOX2 expression induces the exclusion of cytotoxic T cells from the tumor core and promotes resistance to checkpoint blockade therapy. CD8+ T cell exclusion was dependent on regulatory T cell-mediated suppression of tumor vasculature. Depleting tumor-infiltrating regulatory T cells via Glucocorticoid-Induced TNFR-Related (GITR) restored CD8+ T cell infiltration and reduced tumor growth in combination with checkpoint blockade therapy. SignificanceWe identified tumor cell-intrinsic SOX2 expression in lung cancer as a mechanism of resistance to immunotherapy. SOX2 expression increases regulatory T cell populations in the TME, negatively affecting the tumor vasculature and blunting CD8+ T cell infiltration into the tumor core. This effect could be reverted by targeting regulatory T cells with anti-GITR therapy.

immunology↗

bioRxiv2018

Recombinant expression of Proteorhodopsin and biofilm regulators in Escherichia coli for nanoparticle binding and removal in a wastewater treatment model

The small size of nanoparticles is both an advantage and a problem. Their high surface-area-to-volume ratio enables novel medical, industrial, and commercial applications. However, their small size also allows them to evade conventional filtration during water treatment, posing health risks to humans, plants, and aquatic life. This project aims to remove nanoparticles during wastewater treatment using genetically modified Escherichia coli in two ways: 1) binding citrate-capped nanoparticles with the membrane protein Proteorhodopsin, and 2) trapping nanoparticles using Escherichia coli biofilm produced by overexpressing two regulators: OmpR234 and CsgD. We demonstrate experimentally that Escherichia coli expressing Proteorhodopsin binds to 60 nm citrate-capped silver nanoparticles. We also successfully upregulate biofilm production and show that Escherichia coli biofilms are able to trap 30 nm gold particles. Finally, both Proteorhodopsin and biofilm approaches are able to bind and remove nanoparticles in simulated wastewater treatment tanks. We envision integrating our trapping system in both rural and urban wastewater treatment plants to efficiently capture all nanoparticles before treated water is released into the environment.\n\nFinancial DisclosureThis work was funded by the Taipei American School. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.\n\nCompeting InterestsThe authors have declared that no competing interests exist.\n\nEthics StatementN/A\n\nData AvailabilityYes - all data are fully available without restriction. Sequences for the plasmids used in this study are available through the Registry of Standard Biological Parts. Links to raw data are included in Supplementary Information.

synthetic biology↗