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Vol 55(2021) N 6 p. 870-883; DOI 10.1134/S0026893321050162 Full Text

S. Mauran1, N.T. Perera2, I.C. Perera1*

MxyR of Mycobacterium tuberculosis Responds to Xylan; an Unusual Ligand for a MarR Family Transcriptional Regulator

1Synthetic Biology Laboratory, Department of Zoology and Environment Sciences, Faculty of Science, University of Colombo, Colombo 03, Sri Lanka
2Department of Chemistry, Faculty of Applied Sciences, University of Sri Jayewardenepura, Nugegoda, Sri Lanka

*icperera@sci.cmb.ac.lk
Received - 2021-02-19; Revised - 2021-04-12; Accepted - 2021-04-28

Among the repertoire of MarR family transcriptional regulators in Mycobacterium tuberculosis, gene rv3095 (mxyR) encodes Mycobacterial Xylan Regulator, MxyR. Gene mxyR is divergently oriented from a hydrolase (rv3094c), oxidoreductase (rv3093c) and an ABC transporter (rv3092c) and convergently oriented with xylanase (rv3096). Xylanase is commonly used by plant pathogenic microbes where they degrade xylan, the major component of hemicellulose. We have purified the transcriptional regulatory protein encoded by rv3095 and its molecular interactions were studied in detail using electrophoretic mobility shift assay. MxyR interacts with its upstream intergenic region mxyO with high specificity and at a dissociation constant of 5.01 ± 0.017 nM. Notably, this binding is attenuated by specific carbohydrate ligands such as xylan, L-Arabinose and D-Galactose with an IC50 values of 22.7 ± 1.02 ng/μL, 360.8 ± 24.25 ng/μL and 2320.0 ± 96.97 μg/μL, respectively. Consequently, it is evident that this association changes the conformation of the DNA binding helix α4 making the transcriptional regulator incompatible with binding to its cognate DNA, allowing xylanase and other genes to be transcribed. This study establishes the natural ligands of MxyR of M. tuberculosis providing insight on metabolic regulation of the carbohydrate, xylan.

tuberculosis, Mycobacterium tuberculosis, transcriptional regulator, DNA binding, carbohydrate ligands, xylan



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