Biology subjects

Appleby, M.

Publications and source records attributed to Appleby, M..

2 recordsLinked to original sources

bioRxiv2025

Time-resolved structures of β2-adrenergic receptor modulation by a photoswitchable beta-blocker

G protein-coupled receptors (GPCRs) regulate essential physiological responses and are important drug targets, yet their ligand-induced conformational dynamics remain poorly understood. The {beta}2-adrenergic receptor ({beta}2AR) is a prominent member of the GPCR family. It regulates bronchial and vascular function and is a significant drug target, particularly in respiratory and smooth muscle-related disorders. We employed time-resolved crystallography at X-ray free-electron lasers (XFELs) to capture the conformational dynamics of {beta}2AR bound to photoazolol-1, a beta-blocker derivative developed for photopharmacological applications. Structural snapshots of the receptor bound to trans-photoazolol-1 (pre-photoconversion), a strained intermediate, and the fully photoisomerized cis-photoazolol-1 reveal an intricate interplay between ligand chemistry and receptor plasticity. Isomerization of the azobenzene moiety induces distinct conformational changes within the orthosteric pocket, altering interactions with the extracellular loop 2 and transmembrane helices 5 and 6. Supported by functional assays, these structural shifts suggest that photoazolol-1 transitions from an inverse agonist to a neutral antagonist upon photoactivation. Our findings uncover a mechanism of GPCR modulation reminiscent of rhodopsin activation and offer a framework for designing ligands that harness light-driven transitions to achieve spatiotemporal control of receptor function.

biochemistry↗

bioRxiv2025

Integrated structural dynamics uncover new modes of B12 photoreceptor activation

Photoreceptor proteins initiate, regulate and control fundamental biological processes such as vision, photosynthesis and circadian rhythms1. A large photoreceptor subfamily uses vitamin B12 derivatives for light sensing2, contrasting with the well-established mode of action of these organometallic derivatives in thermally activated enzymatic reactions3. The molecular mechanism of B12 photoreception and how this differs to the thermal pathways remain unknown. Here we provide a detailed spatio-temporal description of photoactivation in the prototypical tetrameric B12 photoreceptor CarH4,5 from nanoseconds to seconds by using an integrative approach, combining time- and temperature-resolved structural and spectroscopic methods with quantum chemical calculations. High resolution structural snapshots of key intermediates illustrate how photocleavage of a Co-C bond triggers a pathway of structural changes that propagate throughout CarH from the B12 chromophore, via a previously unknown adduct, to finally cause tetramer dissociation. These unique intermediates, which differentiate CarH from thermally-activated B12 enzymes, steer the photoactivation pathway and act as the molecular bridge between photochemical and photobiological timescales. Our results offer a spatio-temporal understanding of CarH photoactivation and pave the way for designing and optimising B12-dependent photoreceptors for future optogenetic applications.

biophysics↗