Ribosome-dependent Vibrio cholerae mRNAse HigB2 is regulated by a β-strand sliding mechanism.
Toxin-antitoxin (TA) modules are small operons involved in bacterial stress response and persistence. higBA operons form a family of TA modules with an inverted gene organization and a toxin belonging to the RelE/ParE superfamily. Here, we present the crystal structures of chromosomally encoded Vibrio cholerae antitoxin (VcHigA2), toxin (VcHigB2) and their complex, which show significant differences in structure and mechanisms of function compared to the higBA module from plasmid Rts1, the defining member of the family. The VcHigB2 is more closely related to Escherichia coli RelE both in terms of overall structure and the organization of its active site. VcHigB2 is neutralized by VcHigA2, a modular protein with an N-terminal intrinsically disordered toxin-neutralizing segment followed by a C-terminal helix-turn-helix dimerization and DNA binding domain. VcHigA2 binds VcHigB2 with picomolar affinity, which is mainly a consequence of entropically favorable de-solvation of a large hydrophobic binding interface and enthalpically favorable folding of the N-terminal domain into an α-helix followed by a β-strand. This interaction displaces helix α3 of VcHigB2 and at the same time induces a one-residue shift in the register of β-strand β3, thereby flipping the catalytically important Arg64 out of the active site.
Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050 Brussel, Belgium.|Molecular Recognition Unit, Center for Structural Biology, Vlaams Instituut voor Biotechnologie, B-1050 Brussel, Belgium.|Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia.
San
S
Hadži
Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050 Brussel, Belgium.|Biologie Structurale et Biophysique, IBMM-DBM, Université Libre de Bruxelles (ULB), B-6041 Gosselies, Belgium.
Abel
A
Garcia-Pino
Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050 Brussel, Belgium.|Molecular Recognition Unit, Center for Structural Biology, Vlaams Instituut voor Biotechnologie, B-1050 Brussel, Belgium.
Sarah
S
Haesaerts
Biologie Structurale et Biophysique, IBMM-DBM, Université Libre de Bruxelles (ULB), B-6041 Gosselies, Belgium.
Dukas
D
Jurenas
Department of Biology, University of Copenhagen, DK-2200 Copenhagen, Denmark.
Kenn
K
Gerdes
Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia.
Jurij
J
Lah
Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, B-1050 Brussel, Belgium.|Molecular Recognition Unit, Center for Structural Biology, Vlaams Instituut voor Biotechnologie, B-1050 Brussel, Belgium.
Remy
R
Loris
D000992:Antitoxins / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D027101:DNA Topoisomerase IV / Q000235:genetics; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000235:genetics; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D000072757:Protein Conformation, beta-Strand; D055503:Protein Multimerization; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D012260:Ribonucleases / Q000737:chemistry* / Q000235:genetics*; D012270:Ribosomes / Q000737:chemistry / Q000235:genetics; D014734:Vibrio cholerae / Q000737:chemistry / Q000201:enzymology
D000992:Antitoxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D046912:Multiprotein Complexes; D012333:RNA, Messenger; C465566:RelE protein, E coli; D012260:Ribonucleases; D027101:DNA Topoisomerase IV