Controlling protein stability with SULI, a highly sensitive tag for stabilization upon light induction

Light-Induced Nanobody-Mediated Targeted Protein Degradation for Metabolic Flux Control

In metabolic engineering, increasing chemical production usually involves manipulating the expression levels of key enzymes. However, limited synthetic tools exist for modulating enzyme activity beyond the transcription level. Inspired by natural post-translational mechanisms, we present targeted enzyme degradation mediated by optically controlled nanobodies. We applied this method to a branched biosynthetic pathway, deoxyviolacein, and observed enhanced product specificity and yield. We then extend the biosynthesis pathway to violacein and show how simultaneous degradation of two target enzymes can further shift production profiles. Through the redirection of metabolic flux, we demonstrate how targeted enzyme degradation can be used to minimize unwanted intermediates and boost the formation of desired products.

Truncation mutations of CRYGD gene in congenital cataracts cause protein aggregation by disrupting the structural stability of γD-crystallin

Congenital cataracts, a prevalent cause of blindness in children, are associated with protein aggregation. γD-crystallin, essential for sustaining lens transparency, exists as a monomer and exhibits excellent structural stability. In our cohort, we identified a nonsense mutation (c.451_452insGACT, p.Y151X) in the CRYGD gene. To explore the effect of truncation mutations on the structure of γD-crystallin, we examined the Y151X and T160RfsX8 mutations, both located in the Greek key motif 4 at the cellular and protein level in this study. Both truncation mutations induced protein misfolding and resulted in the formation of insoluble aggregates when overexpressed in HLE B3 and HEK 293T cells. Moreover, heat, UV irradiation, and oxidative stress increased the proportion of aggregates of mutants in the cells. We next purified γD-crystallin to estimate its structural changes. Truncation mutations led to conformational disruption and a concomitant decrease in protein solubility. Molecular dynamics simulations further demonstrated that partial deletion of the conserved domain within the Greek key motif 4 markedly compromised the overall stability of the protein structure. Finally, co-expression of α-crystallins facilitated the proper folding of truncated mutants and mitigated protein aggregation. In summary, the structural integrity of the Greek key motif 4 in γD-crystallin is crucial for overall structural stability.

Lighting the way: recent developments and applications in molecular optogenetics

Molecular optogenetics utilizes genetically encoded, light-responsive protein switches to control the function of molecular processes. Over the last two years, there have been notable advances in the development of novel optogenetic switches, their utilization in elucidating intricate signaling pathways, and their progress toward practical applications in biotechnological processes, material sciences, and therapeutic applications. In this review, we discuss these areas, offer insights into recent developments, and contemplate future directions.

Rapid Formation of Intramolecular Disulfide Bridges using Light: An Efficient Method to Control the Conformation and Function of Bioactive Peptides

Disulfide bonds are widely found in natural peptides and play a pivotal role in stabilizing their secondary structures, which are highly associated with their biological functions. Herein, we introduce a light-mediated strategy to effectively control the formation of disulfides. Our strategy is based on 2-nitroveratryl (oNv), a widely used photolabile motif, which serves both as a photocaging group and an oxidant (after photolysis). We demonstrated that irradiation of oNv-caged thiols with UV light could release free thiols that are rapidly oxidized by locally released byproduct nitrosoarene, leading to a "break-to-bond" fashion. This strategy is highlighted by the in situ restoration of the antimicrobial peptide tachyplesin I (TPI) from its external disulfide-caged analogue TPI-1. TPI-1 exhibits a distorted structure and a diminished function. However, upon irradiation, the β-hairpin structure and membrane activity of TPI were largely restored via rapid intramolecular disulfide formation. Our study proposes a powerful method to regulate the conformation and function of peptides in a spatiotemporal manner, which has significant potential for the design of disulfide-centered light-responsive systems.