Biology subjects

Vallet, A.

Publications and source records attributed to Vallet, A..

4 recordsLinked to original sources

bioRxiv2024

The plastid-encoded RNA polymerase structures a logistic chain for light-induced photosynthesis

The chloroplast is the semi-autonomous organelle of eukaryotes that performs photosynthesis. In higher plants, chloroplast biogenesis depends on a tight transcriptional coordination of both nuclear- and-plastid photosynthesis-associated genes. The plastid-encoded RNA-polymerase (PEP) is composed of a plastid-encoded catalytic core, similar to multi-subunit RNA polymerases, bound to fifteen nuclear-encoded PEP-associated proteins (PAPs). The binding of all the PAPs to the catalytic core is essential for plastid transcription of photosynthesis-associated genes. Our cryo-electron microscopy structure of the native 21-subunit PEP from Sinapis alba reveals the distinctive patterning of PAP interactions, which evolved upon the ancestral cyanobacterial catalytic core acting as a scaffold. Using PAP8 in planta as bait for affinity purification and proximity labeling, we provide the protein landscapes surrounding the PEP and other PAP8-interacting complexes at the transition from skotomorphogenesis to photomorphogenesis. The data highlight multiple functional couplings in which plastid transcription is at the beginning of a spatial logistic chain, extending from transcription to the assembly of the photosynthetic apparatus into the thylakoids. In addition, dark-specific interactions between photoreceptors and PAP8 establish a physical link between an integrated light signaling and plastid functions.

plant biology↗

bioRxiv2023

A single domain intrabody targeting the follicle-stimulating hormone receptor (FSHR) impacts FSH-induced G protein-dependent signalling

Intracellular variable fragments from heavy-chain antibody from camelids (intra-VHH) have been successfully used as chaperones to solve the 3D structure of active G protein-coupled receptors bound to their transducers. However, their effect on signalling has been poorly explored, although they may provide a better understanding on the relationships between receptor conformation and activity. Here, we isolated and characterized iPRC1, the first intra-VHH recognizing a member of the large glycoprotein hormone receptors family, the follicle-stimulating hormone receptor (FSHR). This intra-VHH recognizes the FSHR 3rd intracellular loop and decreases cAMP production in response to FSH, without altering Gs recruitment. Hence, iPRC1 behaves as an allosteric modulator and provides a new tool to complete structure/activity studies performed so far on this receptor.

pharmacology and toxicology↗

bioRxiv2023

Disulfide-bond-induced structural frustrationand dynamic disorder in a peroxiredoxin fromMAS NMR

Disulfide bond formation is fundamentally important for protein structure, and constitutes a key mechanism by which cells regulate the intracellular oxidation state. Peroxiredoxins (PRDXs) eliminate reactive oxygen species such as hydrogen peroxide by using a catalytic cycle of Cys oxidation and reduction. High molecular-weight assemblies of PRDXs have recently been shown to additionally act as molecular chaperones. The consequences of disulfide bonds on the dynamics of these large assemblies are poorly understood. We show that formation of disulfide bonds along the catalytic cycle induces extensive s time scale dynamics, as monitored by magic-angle spinning NMR of the 216 kDa-large Tsa1 decameric assembly and solution-NMR of a designed dimeric mutant. We ascribe the conformational dynamics to structural frustration, resulting from conflicts between the disulfide-constrained reduction of mobility and the desire to fulfil other favorable contacts.

biophysics↗

bioRxiv2022

Sleep cycle-dependent vascular dynamics enhance perivascular cerebrospinal fluid flow and solute transport

Perivascular spaces (PVS) are important highways for fluid and solute transport in the brain enabling efficient waste clearance during sleep. Using two-photon imaging of naturally sleeping mice we demonstrate sleep cycle-dependent PVS dynamics - slow, large-amplitude oscillations in NREM, a reduction in REM and an enlargement upon awakening at the end of a sleep cycle. By biomechanical modeling we demonstrate that these sleep cycle-dependent PVS dynamics drive fluid flow and solute transport.

neuroscience↗