Biology subjects

Lahmy, R.

Publications and source records attributed to Lahmy, R..

3 recordsLinked to original sources

bioRxiv2025

Expanding the Repertoire of Photoswitchable Unnatural Amino Acids for Enzyme Engineering

Photoswitchable unnatural amino acids (psUAAs) play a crucial role in the engineering of light-sensitivity in enzymes, which holds significant promise for diverse applications such as biotherapy and biocatalysis. Besides near-quantitative photoconversion, the success and expediency of a psUAA for a certain application is defined by its interaction potential with the enzyme, its thermal stability and its effective wavelength of irradiation. To establish high versatility in the current repertoire, we have designed and synthesized six psUAAs based on azobenzene, arylazopyrazole, arylazothiazole, hemithioindigo and spiropyran photoswitches. The resulting psUAAs exhibit an enhanced interaction potential within an enzyme owing to their capacity for hydrogen bonding, ionic interactions, and metal ion coordination. Moreover, we observed diverse photochemical behaviors among the psUAAs, with four of them reversibly switching between the isomers with purely visible light. Notably, we identified orthogonal aminoacyl-tRNA synthetases that facilitate the incorporation of five of the six psUAAs co-translationally and computationally analyzed the synthetase-psUAA interactions. Finally, we evaluated the photochemical behavior of the five psUAAs within an enzymatic model and tested the photocontrol of catalysis confirming their diversity. Ultimately, our findings significantly expanded the repertoire of psUAAs and demonstrated their feasibility for enzyme engineering studies.

synthetic biology↗

bioRxiv2024

Promoting enzyme catalysis via azobenzene facilitated vibrational energy transfer

Azobenzene is a widely recognized tool for achieving artificial spatiotemporal control of enzyme activity using light. Photocontrol reversibility is typically based on photostationary states with varying E and Z isomer compositions achieved through irradiation at specific wavelengths. Here, we report an alternative mechanism for azobenzene based enzyme regulation, discovered through simultaneous irradiation with two wavelengths. Using two engineered variants of imidazole glycerol phosphate synthase, in which azobenzene was incorporated as an unnatural amino acid to enable reversible control under monochromatic irradiation, we uncovered unique behavior under dichromatic irradiation. Notably, a distinct spectroscopic signal from the azobenzene moiety emerged during simultaneous irradiation at 365 nm and 420 nm and vanished upon return to the dark. Intriguingly, dichromatic irradiation triggered a reproducible two-fold increase in catalytic activity and an instantaneous return to baseline activity in the dark for one variant. In contrast, the other variant and the wild-type enzyme maintained their baseline activity under the same conditions. These findings reveal an unexplored avenue for azobenzene photoswitching, offering a novel approach to photocontrol with potential applications in sequentially regulating multiple enzymes, especially when combined with monochromatic irradiation strategies.

biophysics↗

bioRxiv2019

A reference map of the human proinsulin biosynthetic interaction network

The beta-cell protein synthetic machinery is dedicated to the production of insulin, which plays a critical role in organismal homeostasis. Insulin synthesis requires the proper folding and trafficking of its precursor, proinsulin, yet the precise network of proinsulin protein interactions in the secretory pathway remains poorly defined. In the present study we conducted unbiased profiling of the proinsulin interactome in human islets, utilizing a human proinsulin-specific monoclonal antibody for affinity purification and mass spectrometry. Stringent analysis identified a central node of interactions between human proinsulin and sequential secretory pathway proteins that is remarkably conserved across 3 ethnicities and both genders. Among the most prominent proinsulin interactions was with ER-localized peroxiredoxin-4 (PRDX4). A functional role for PRDX4 in beta-cells was demonstrated by gene silencing that rendered proinsulin susceptible to misfolding, particularly in response to oxidative stress. Conversely, exogenous PRDX4 improved proinsulin folding. Notably, oxidative stress and even high glucose treatment alone induced proinsulin misfolding in human islets and MIN6 cells, and this was accompanied by sulfonylation of PRDX4, a modification known to inactivate peroxiredoxins. This finding prompted PRDX4 analysis in a panel of human islet samples that revealed significantly higher levels of sulfonylated (inactive) PRDX4 in islets from patients with T2D compared to that of healthy individuals. Taken together, these data highlight the importance of elucidating the complete proinsulin interactome in human islets in order to understand critical steps controlling insulin biosynthesis, beta cell function, and T2D.

biochemistry↗