Structural basis of transcriptional regulation by the HigA antitoxin

• Type of Material: Article
• Authors: Marc C. Schureck, Emory University; Jeffrey Meisner, Emory University; Eric D. Hoffer, Emory University; Dongxue Wang, Emory University; Nina Onuoha, Emory University; Shein Ei Cho, Emory University; John Lollar, Emory University; Christine Dunham, Emory University
• Language: English
• Date: 2019-06-01
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2019 John Wiley & Sons Ltd.
• Final Published Version (URL): http://dx.doi.org/10.1111/mmi.14229
• Title of Journal or Parent Work: Molecular Microbiology
• Volume: 111
• Issue: 6
• Start Page: 1449
• End Page: 1462
• Grant/Funding Information: This work is based upon research conducted at the NE-CAT beamlines, which are funded by the NIGMS from the NIH (P41 GM103403), and at the SER-CAT beamline.; This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02–06CH11357.; This work was supported by in part by a National Science Foundation CAREER award MCB 0953714 (CMD), a National Institutes of Health (NIH) Biochemistry, Cellular and Developmental Biology Graduate Training Grant (5T32GM8367), and a NIH National Research Service Award Fellowship GM108351 (MAS).; The Pilatus 6M detector on 24-ID-C beam line is funded by a NIH-ORIP HEI grant (S10 RR029205).
• Keywords: Crystal structure; Yoeb toxin; Multidrug tolerance; Recognition; Science & Technology; Mechanisms; Killer gene system; Microbiology; Life Sciences & Biomedicine; Sedimentation velocity; Biochemistry & Molecular Biology; Escherrichia coli; YEFM-YOEB; Complex
• Research Categories: Chemistry, Biochemistry; Biology, Molecular; Biology, Microbiology; Biology, Genetics

Abstract

Bacterial toxin–antitoxin systems are important factors implicated in growth inhibition and plasmid maintenance. Type II toxin–antitoxin pairs are regulated at the transcriptional level by the antitoxin itself. Here, we examined how the HigA antitoxin regulates the expression of the Proteus vulgaris higBA toxin–antitoxin operon from the Rts1 plasmid. The HigBA complex adopts a unique architecture suggesting differences in its regulation as compared to classical type II toxin–antitoxin systems. We find that the C-terminus of the HigA antitoxin is required for dimerization and transcriptional repression. Further, the HigA structure reveals that the C terminus is ordered and does not transition between disorder-to-order states upon toxin binding. HigA residue Arg40 recognizes a TpG dinucleotide in higO2, an evolutionary conserved mode of recognition among prokaryotic and eukaryotic transcription factors. Comparison of the HigBA and HigA-higO2 structures reveals the distance between helix-turn-helix motifs of each HigA monomer increases by ~4 Å in order to bind to higO2. Consistent with these data, HigBA binding to each operator is twofold less tight than HigA alone. Together, these data show the HigB toxin does not act as a co-repressor suggesting potential novel regulation in this toxin–antitoxin system.