Biology subjects

Manta, B.

Publications and source records attributed to Manta, B..

4 recordsLinked to original sources

bioRxiv2026

Phenotypic Characterization of OXA-439, an OXA-163 variant, isolated from uropathogenic Escherichia coli

OXA-48-like {beta}-lactamases, such as OXA-163, OXA-181, OXA-405, OXA-505, among others, are class D carbapenem-hydrolyzing enzymes increasingly reported worldwide, yet some variants remain poorly characterized at the phenotypic levels. Here, we report OXA-439, a variant of OXA-163, in a producing uropathogenic Escherichia coli (UPEC) in Uruguay, recovered from a catheter-associated urinary tract infection with discordant routine susceptibility results. The specific contribution of OXA-439, bla-OXA-48, bla-OXA-163, and bla-OXA-439 were cloned into pET24a vector and expressed in Escherichia coli BL21(DE3), and their activity was evaluated by MIC microdilution against a panel of penicillins, ESCs, carbapenems, and {beta}-lactam/{beta}-lactamase inhibitor combinations. OXA-439 exhibited a substrate profile highly similar to OXA-163 conferring resistance to piperacillin and third-generation cephalosporins while remaining susceptible to carbapenems but with globally reduced MIC values and a complete loss of activity toward amoxicillin and clavulanate. These data suggest that the Y123H substitution, located near the catalytic Ser70/Lys73 region, subtly perturbs the active-site environment and decreases penicillinase efficiency.

microbiology↗

bioRxiv2026

Mass spectrometric analysis of free methionine oxidation levels in E. coli

Oxidation of free methionine plays important roles in cellular redox homeostasis, yet its accurate quantification has been hindered by methodological challenges. Here, we introduce free Methionine Oxidation by Blocking (fMObB), a mass spectrometry-based method that enables accurate measurement of the fractional oxidation of free methionines. Applying fMObB to Escherichia coli, we quantify free methionine oxidation under basal and oxidative stress conditions, and in strains lacking methionine sulfoxide reductases. We find that during oxidative stress, free methionines exhibit higher oxidation levels than protein-bound methionines and that methionine sulfoxide reductases play a central role in maintaining reduced free methionine pools. Together, this work establishes fMObB as a generalizable strategy for probing free methionine redox states in cellular systems.

biochemistry↗

bioRxiv2025

Methionine sulfoxide reductase B3 antioxidant activity is indispensable for mouse inner ear cuticular plate structure and hair bundle integrity

Methionine sulfoxide reductases (MSR) are enzymes responsible for catalyzing the reduction of methionine-sulfoxides. We previously demonstrated that variants in human MSRB3, a member of the MSR family, are associated with profound autosomal recessive prelingual non-syndromic hearing loss DFNB74. To better understand the role of MSRB3 in the auditory pathway, we generated a complete MsrB3 gene knock-out mouse model of human DFNB74 deafness. The MsrB3 deficient mouse showed profound hearing loss by postnatal day 16 (P16), which was accompanied by hair cell morphological abnormalities including altered stereocilia bundle shape and cuticular plate degeneration followed by hair cell apoptotic death. Although the absence of MSRB3 primarily affected the actin cytoskeleton, rootlets were present, and the expression and localization of major F-actin stereocilia-core proteins were unaltered. Biochemical assays demonstrated that wild-type MSRB3, but not MSRB3 harboring p.Cys89Gly, the same variant reported for human deafness DFNB74, can repolymerize oxidized actin. Consistent with these in vitro data, we observed a decreased ratio of reduced/total actin in the inner ears of Msrb3 knock-out mice. These data suggest a protective role of MSRB3 in the maintenance and maturation of stereocilia and hair cells, a conserved mechanism aimed at maintaining actin redox dynamics in these sensory cells.

genetics↗

bioRxiv2020

An NMR-based biosensor to measure stereo-specific methionine sulfoxide reductase (MSR) activities in vitro and in vivo.

Oxidation of protein methionines to methionine-sulfoxides (MetOx) is associated with several age-related diseases. In healthy cells, MetOx is reduced to methionine by two families of conserved methionine sulfoxide reductase enzymes, MSRA and MSRB that specifically target the S- or R-diastereoisomers of methionine-sulfoxides, respectively. To directly interrogate MSRA and MSRB functions in cellular settings, we developed an NMR-based biosensor that we call CarMetOx to simultaneously measure both enzyme activities in single reaction setups. We demonstrate the suitability of our strategy to delineate MSR functions in complex biological environments that range from native cell lysates to zebrafish embryos. Thereby, we establish differences in substrate specificities between prokaryotic and eukaryotic MSRs and introduce CarMetOx as a highly sensitive tool for studying therapeutic targets of oxidative stress-related human diseases and redox regulated signaling pathways. Our approach further extends high-resolution in-cell NMR measurements of exogenously delivered biomolecules to an entire multicellular organism.

biophysics↗