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Publication Abstract from PubMed

In toxin-antitoxin systems, many antitoxin proteins that neutralize their cognate toxin proteins also bind to DNA to repress transcription, and the DNA-binding affinity of the antitoxin is affected by its toxin. We solved crystal structures of the antitoxin HigA (apo-(Sf)HigA) and its complex with the toxin HigB ((Sf)HigBA) from Shigella flexneri. The apo-(Sf)HigA shows a distinctive V-shaped homodimeric conformation with sequestered N-domains having a novel fold. (Sf)HigBA appears as a heterotetramer formed by N-terminal dimerization of (Sf)HigB-bound (Sf)HigA molecules. The conformational change in (Sf)HigA upon (Sf)HigB binding is mediated by rigid-body movements of its C-domains, which accompanied an overall conformational change from wide V-shaped to narrow V-shaped dimer. Consequently, the two putative DNA-binding helices (alpha7 in each subunit) are repositioned to a conformation more compatible with canonical homodimeric DNA-binding proteins containing HTH motifs. Collectively, this study demonstrates a conformational change in an antitoxin protein, which occurs upon toxin binding and is responsible for regulating antitoxin DNA binding.

Structural changes of antitoxin HigA from Shigella flexneri by binding of its cognate toxin HigB.,Yoon WS, Seok SH, Won HS, Cho T, Lee SJ, Seo MD Int J Biol Macromol. 2019 Jun 1;130:99-108. doi: 10.1016/j.ijbiomac.2019.02.111. , Epub 2019 Feb 21. PMID:30797012^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.