Biology subjects

Aran, M.

Publications and source records attributed to Aran, M..

3 recordsLinked to original sources

bioRxiv2025

Metabolic reshaping drives novel melanin production from tryptophan in a cystic fibrosis Pseudomonas aeruginosa clinical isolate

Pseudomonas aeruginosa is a human opportunistic pathogen, capable of producing a wide range of metabolites, including pyomelanin. This pigment results from alterations in tyrosine catabolism. Melanin synthesis from tryptophan has never been reported in Pseudomonas. In this study, we describe a tryptophan-derived melanin in P. aeruginosa PAH, a strain that was isolated from a fibrocystic patient. PAH produced a brown pigment when grown in LB or L-tryptophan-supplemented media. Structural analysis revealed this pigment was composed by two fractions differing in NaOH solubility: a soluble one consistent of pyomelanin, and an insoluble fraction with a complex structure containing substituted indolic units. A pyomelanin inhibitor enhanced total melanin synthesis, mainly the insoluble fraction, and a tryptophan 2,3-dioxygenase inhibitor decreased pigment formation. Metabolomic profiling identified distinct indolic compounds and low levels of anthranilate in PAH cultures. Genomic and transcriptomic analyses revealed the presence of mutations and downregulation of genes related to pyoverdine biosynthesis. Furthermore, iron supplementation in the culture medium reduced melanin production. Overall, tryptophan arises as a key compound for melanin production in PAH, expanding the diversity of melanins synthesized by this genus. Furthermore, iron deprivation emerges as a critical factor triggering melanin biosynthesis, probably as a survival strategy enabling persistence in the fibrocystic lung environment.

microbiology↗

bioRxiv2023

Molten globule driven and self-downmodulated phase separation of a viral factory scaffold

Viral factories of liquid-like nature host transcription and replication in most viruses. The syncytial respiratory virus factories include gene function proteins, brought together by the phosphoprotein (P) RNA polymerase cofactor, present across non-segmented negative stranded RNA viruses. Homotypic liquid-liquid phase separation of RSV-P is governed by an -helical molten globule domain, and strongly self-downmodulated by adjacent sequences. Condensation of P with the nucleoprotein N is stoichiometrically tuned, defining aggregate-droplet and droplet-dissolution boundaries. Time course analysis show small N-P nuclei gradually coalescing into large granules in transfected cells. This behavior is recapitulated in infection, with small puncta evolving to large viral factories, strongly suggesting that P-N nucleation-condensation sequentially drives viral factories. Thus, the tendency of P to undergo phase separation is moderate and latent in the full-length protein but unleashed in the presence of N or when neighboring disordered sequences are deleted. This, together with its capacity to rescue nucleoprotein-RNA aggregates suggests a role as a "solvent-protein" and possible fluidity tuner of viral factories.

biophysics↗

bioRxiv2022

Selection of Synthetic Proteins to Modulate the Human Frataxin Function

Frataxin is a kinetic activator of the mitochondrial supercomplex for iron-sulfur cluster assembly. Low frataxin expression or a decrease in its functionality results in Friedreichs Ataxia (FRDA). With the aim of creating new molecular tools to study this metabolic pathway, and ultimately, to explore new therapeutic strategies, we have investigated the possibility of obtaining small proteins exhibiting a high affinity for frataxin. In this study, we applied the ribosome display approach, using human frataxin as the target. We focused on Affi_224, one of the proteins that we were able to select after five selection rounds. We have studied the interaction between both proteins and discussed some applications of this specific molecular tutor, concerning the modulation of supercomplex activity. Affi_224 and frataxin showed a KD value in the nanomolar range, as judged by surface plasmon resonance analysis. Most likely, it binds to the frataxin acidic ridge, as suggested by the analysis of chemical shift perturbations (NMR) and computational simulations. Affi_224 was able to increase Cys NFS1 desulfurase activation exerted by the FRDA frataxin variant G130V. Our results suggest quaternary addition may be a new tool to modulate frataxin function in vivo. Nevertheless, more functional experiments under physiological conditions should be carried out to evaluate Affi_224 effectiveness in FRDA cell models.

biochemistry↗