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Proc. Natl. Acad. Sci. USA, Published ahead of print February 7, 2019 | https://doi.org/10.1073/pnas.1811509116 Structural basis for HOCl recognition and regulation mechanisms of HypT, a hypochlorite-specific transcriptional regulator

Inseong Jo^a,b,c,d,1, Dajeong Kim^a,b,c,d,1, Taehoon No^a,b,c,d, Seokho Hong^a,b,c,d, Jinsook Ahn^a,b,c,d, Sangryeol Ryu^a,b,c,d,2, and Nam-Chul Ha^a,b,c,d,2

^a Department of Agricultural Biotechnology, Seoul National University, 08826 Seoul, Republic of Korea; ^bCenter for Food Safety and Toxicology, Seoul National University, 08826 Seoul, Republic of Korea; ^c Center for Food and Bioconvergence, Seoul National University, 08826 Seoul, Republic of Korea; and ^d Research Institute for Agriculture and Life Sciences, Seoul National University, 08826 Seoul, Republic of Korea

¹I.J. and D.K. contributed equally to this work.
²To whom correspondence may be addressed.

Abstract

Hypochlorous acid (HOCl) is generated in the immune system to kill microorganisms. In Escherichia coli, a hypochlorite-specific transcription regulator, HypT, has been characterized. HypT belongs to the LysR-type transcriptional regulator (LTTR) family that contains a DNA-binding domain (DBD) and a regulatory domain (RD). Here, we identified a hypT gene from Salmonella enterica serovar Typhimurium and determined crystal structures of the full-length HypT protein and the RD. The full-length structure reveals a type of tetrameric assembly in the LTTR family. Based on HOCl-bound and oxidation-mimicking structures, we identified a HOCl-driven methionine oxidation mechanism, in which the bound HOCl oxidizes a conserved methionine residue lining the putative ligand-binding site in the RD. Furthermore, we proposed a molecular model for the oxidized HypT, where methionine oxidation by HOCl results in a conformational change of the RD, inducing a counter rotation of the DBD dimers. Target genes that are regulated by HypT and their roles in Salmonella were also investigated. DNase I footprinting experiments revealed a DNA segment containing two pseudopalindromic motifs that are separated by ∼100 bp, suggesting that only the oxidized structure makes a concomitant binding, forming a DNA loop. An understanding of the HypT-mediated mechanism would be helpful for controlling many pathogenic bacteria by counteracting bacterial HOCl defense mechanisms.

hypochlorous acid | LysR-type transcription regulator | HypT | methionine oxidation | repression mechanism

논문정보

형식Research article
게재일2019년 02월 (BRIC 등록일 2019-02-21)
연구진국내 연구진
분야 생명과학 > 분자생물학

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