Biology subjects

Brkic, A.

Publications and source records attributed to Brkic, A..

3 recordsLinked to original sources

bioRxiv2026

C-terminal evolutionary remodelling of isoleucyl-tRNA synthetases is a prokaryote-specific strategy for tuning aminoacylation rate

Aminoacyl-tRNA synthetases are the guardians of translational fidelity. Their complex function is mirrored by an elaborate structure, which includes multiple nested domains. While the evolutionary pressures that promoted the emergence of some domains, such as the editing domain, are clear, the pressures acting on other domains, particularly those at the C-terminus, are not. Here, we use a combination of kinetic analysis, X-ray crystallography, and bioinformatics to unveil the history and evolutionary forces that have shaped isoleucyl-tRNA synthetase (IleRS) domain structure. We find that the traditional classification into IleRS1 and IleRS2, based on the C-terminal tRNA-recognition domains, is incomplete, as it fails to capture features of the synthetic domain. Guided by the crystal structure of the Priestia megaterium IleRS2:tRNA complex, we removed key interactions between IleRS2 and its cognate tRNA and characterised their impact on enzyme activity. We found that D-loop interactions with the IleRS2 C-terminal region are non-essential in prokaryotes, and their loss can even increase catalytic turnover. Further, the zinc-binding domain of IleRS1 recognises the anticodon less stringently than the canonical C-terminal domain of IleRS2. Our data suggest that C-terminal evolutionary remodelling of IleRSs is an ongoing process with a historical precedent, consistent with selection for faster aminoacylation rate.

biochemistry↗

bioRxiv2023

Antibiotic hyper-resistance in a class I aminoacyl-tRNA synthetase with altered active site signature motif

Antibiotics target key biological processes that include protein synthesis. Bacteria respond by developing resistance, which increases rapidly due to antibiotics overuse. Mupirocin, a clinically used natural antibiotic, inhibits isoleucyl-tRNA synthetase (IleRS), an enzyme that links isoleucine to its tRNAIle for protein synthesis. Two IleRSs, mupirocin-sensitive IleRS1 and resistant IleRS2, coexist in bacteria. The latter may also be found in resistant Staphylococcus aureus clinical isolates. Here, we describe the structural basis of mupirocin resistance and unravel a mechanism of hyper-resistance evolved by some IleRS2 proteins. We surprisingly find that an up to 103-fold increase in resistance originates from alteration of the HIGH motif, a signature motif of the class I aminoacyl-tRNA synthetases to which IleRSs belong. The structural analysis demonstrates how an altered HIGH motif could be adopted in IleRS2 but not IleRS1, providing insight into an elegant mechanism for coevolution of the key catalytic motif and associated antibiotic resistance.

biochemistry↗

bioRxiv2019

Genomewide analysis of biomass responses to water withholding in young plants of maize inbred lines with expired plant variety protection certificate

Patterns of seasonal variations in rainfall are changing which affects rain-fed agricultural areas. Water deficit during the early vegetative growth poses threat as it causes variability in plant development, makes plant susceptible to other stresses and deteriorates the stands. Plants responses to water deficit are reflected in biomass traits which represent the morpho-physiological adjustments of plant to new conditions. The aims of this study were to assess the biomass responses of maize inbred lines with expired plant variety protection certificate that are freely distributed worldwide using genomewide analysis approach. The collection of 109 maize inbred lines, genotyped using genotyping-by-sequencing, was planted in controlled conditions (16/8 day/night, 25{degrees}C, 50% RH, 200 Mol/m2/s) in trays filled with soil in three replicates. Plants in control (C) were watered every two days with 8 mlH2O, while watering was stopped for 10 days in water withholding (WW) treatment. Fourteen days old plants were harvested and fresh weight (FW), dry weight (DW) and dry matter content (DMC, % of FW) were measured. Different responses to WW were detected in two genetic subgroups: Stiff Stalk and Non-Stiff Stalk. Totally 29 QTLs were detected, and it was shown that genetic regulation of DMC is different than regulation of FW and DW. This was further supported with correlations of rrBLUP marker effects among the traits. It was concluded that measurements of biomass traits in this manner are fast and reliable indicator of plants response to water deficit and can be used for effective screening of breeding progenies.

genetics↗