Biology subjects

Corrales-Guerrero, L.

Publications and source records attributed to Corrales-Guerrero, L..

4 recordsLinked to original sources

bioRxiv2026

The cyanobacterium Anabaena uses pleomorphism as an acclimation strategy to high light stress

O_LIPhytoplankton species display characteristic morphologies that are generally assumed to confer adaptive advantages, yet the functional significance of cell shape remains poorly understood. Here, we investigated whether pleomorphism contributes to acclimation to changing light environments. C_LIO_LIUsing the cyanobacterium Anabaena sp. PCC 7120 as a model system, we combined molecular genetics, microscopy, physiological measurements and biophysical analyses to determine how morphology is regulated and how it affects photosynthetic performance under different light intensities. C_LIO_LIWe show that Anabaena undergoes a reversible light-dependent morphological transition from rod-shaped cells under low light to large globular cells under high light stress. This transition is controlled by the relative activities of the elongasome and class A penicillin-binding proteins and is accompanied by thylakoid reorganization. The globular morphology reduces light absorption and enables cells to maintain photosynthetic activity under photoinhibitory conditions. C_LIO_LIOur findings establish a mechanistic link between cell-wall remodelling, cellular optics and photosynthetic performance, revealing pleomorphism as a dynamic acclimation strategy to high light stress. More broadly, this work provides experimental support for the packaging effect and highlights morphology as an active determinant of phytoplankton fitness. C_LI

plant biology↗

bioRxiv2025

Allosteric modulation of TIA-1 phase separation by double serine phosphorylation

In response to diverse harmful stimuli, eukaryotic cells generate cytoplasmic stress granules (SGs), mainly composed of mRNAs and RNA-binding proteins (RBPs). RBPs are fine-tuned by a diverse array of post-translational modifications (PTMs), with important consequences for the assembly, dynamics and clearance of SGs. One of the best characterized SG nucleators is the RBP T-cell intracellular antigen 1 (TIA-1), although knowledge about the structural and functional impact of its identified PTMs is very limited. TIA-1 is organized into three RNA-recognition motifs (RRMs) and a C-terminal prion-related domain (PRD) that drives its phase separation from the cytosol. Here, we analyzed the effect of TIA-1 double phosphorylation in RRM3, at serines 198 and 199. Microscopic observations revealed an increased propensity of the phosphomimetic TIA-1 S198/199E to undergo liquid-liquid phase separation (LLPS) and self-assemble into SGs independently of stress stimuli. Our computational simulations, supported by NMR data, have suggested that such phosphorylations promote the formation of a {beta}-hairpin motif at the beginning of the PRD. Moreover, the ALS-associated mutation V283M in TIA-1 was predicted to lead to the formation of an aberrant structure in the {beta}-hairpin region, highlighting the fine balance between physiological and pathogenic TIA-1 phase transition, and the importance of a better understanding of the molecular mechanisms underlying the liquid demixing of this RBP.

biophysics↗

bioRxiv2021

The CTPase activity of ParB acts as a timing mechanism to control the dynamics and function of prokaryotic DNA partition complexes

DNA partitioning CTPases of the ParB family mediate the segregation of bacterial chromosomes and low-copy number plasmids. They act as DNA-sliding clamps that are loaded at parS motifs in the centromeric region of target DNA molecules and then spread laterally to form large nucleoprotein complexes that serve as docking points for the DNA segregation machinery. Here, we identify conformational changes that underlie the CTP- and parS-dependent closure of ParB clamps. Moreover, we solve crystal structures of ParB in the pre- and post-hydrolysis state and provide insights into the catalytic mechanism underlying nucleotide hydrolysis. The characterization of CTPase-deficient ParB variants reveals that CTP hydrolysis serves as a timing mechanism to control the sliding time of ParB. Hyperstable clamps are trapped on the DNA, leading to excessing spreading and severe chromosome segregation defects in vivo. These findings clarify the role of the ParB CTPase cycle in partition complex dynamics and function and thus complete our understanding of this prototypic CTP-dependent molecular switch.

microbiology↗

bioRxiv2019

Molecular architecture of the DNA-binding sites of the P-loop ATPases MipZ and ParA from Caulobacter crescentus

Two related P-loop ATPases, ParA and MipZ, mediate the spatiotemporal regulation of chromosome segregation and cell division in Caulobacter crescentus. Both of these proteins share the ability to form dynamic concentration gradients that control the positioning of regulatory targets within the cell. Their proper localization relies on their nucleotide-dependent cycling between a monomeric and a dimeric state, driven by interaction with the chromosome partitioning protein ParB, and on the ability of the dimeric species to associate non-specifically with the nucleoid. In this study, we use a combination of genetic screening, biochemical analysis and hydrogen/deuterium exchange mass spectrometry to identify the residues mediating the interaction of MipZ with DNA. Our results show that the DNA-binding activity of MipZ relies on a series of positively charged and hydrophobic residues lining both sides of the dimer interface. MipZ thus appears to associate with DNA in a sequence-independent manner through electrostatic interactions with the DNA phosphate backbone. In support of this hypothesis, chromatin immunoprecipitation analyses did not reveal any specific target sites in vivo. When extending our analysis to ParA, we found that the architectures of the MipZ and ParA DNA-binding sites are markedly different, although their relative positions on the dimer surface and their mode of DNA binding are conserved. Importantly, bioinformatic analysis suggests that the same principles apply to other members of the P-loop ATPase family. ParA-like ATPases thus share common mechanistic features, although their modes of action have diverged considerably during the course of evolution.\n\nSIGNIFICANCEParA-like P-loop ATPases are involved in a variety of cellular processes in bacteria, including chromosome and plasmid segregation, chemoreceptor and carboxysome positioning, and division site placement. Many members of this large protein family depend on the ability to bind non-specific DNA for proper function. Although previous studies have yielded insights in the DNA-binding properties of some ParA-like ATPases, a comprehensive view of the underlying mechanisms is still lacking. Here, we combine state-of-the-art cell biological, biochemical and biophysical approaches to localize the DNA-binding regions of the ParA-like ATPases MipZ and ParA from Caulobacter crescentus. We show that the two proteins use the same interface and mode of action to associate with DNA, suggesting that the mechanistic basis of DNA binding may be conserved in the ParA-like ATPase family.

microbiology↗