title: The structural mechanism of the inhibition of archaeal RelE toxin by its cognate RelB antitoxin.
abstract: The archaeal toxin, aRelE, in the hyperthermophilic archaeon Pyrococcus horikoshii OT3 inhibits protein synthesis, whereas its cognate antitoxin, aRelB, neutralizes aRelE activity by forming a non-toxic complex, aRelB-aRelE. The structural mechanism whereby aRelB neutralizes aRelE activity was examined by biochemical and biophysical analyses. Overexpression of aRelB with an aRelE mutant (ΔC6), in which the C-terminal residues critical for aRelE activity were deleted, in Escherichia coli allowed a stable complex, aRelB-ΔC6, to be purified. Isothermal titration of aRelE or ΔC6 with aRelB indicated that the association constant (Ka) of wild-type aRelB-aRelE is similar to that of aRelB-ΔC6, demonstrating that aRelB makes little contact with the C-terminal active site of aRelE. Overexpression of deletion mutants of aRelB with aRelE indicated that either the N-terminal (pos. 1-27) or C-terminal (pos. 50-67) fragment of aRelB is sufficient to counteract the toxicity of aRelE in E. coli cells and the second α-helix (α2) in aRelB plays a critical role in forming a stable complex with aRelE. The present results demonstrate that aRelB, as expected from its X-ray structure, precludes aRelE from entering the ribosome, wrapping around the molecular surface of aRelE.
authors: Laboratory of Biochemistry, Department of Bioscience and Biotechnology, Graduate School, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan.
authors: Masaaki
authors: M
authors: Shinohara
authors: Jin Xu
authors: JX
authors: Guo
authors: Misako
authors: M
authors: Mori
authors: Takashi
authors: T
authors: Nakashima
authors: Hisanori
authors: H
authors: Takagi
authors: Etsuko
authors: E
authors: Nishimoto
authors: Shoji
authors: S
authors: Yamashita
authors: Kouhei
authors: K
authors: Tsumoto
authors: Yoshimitsu
authors: Y
authors: Kakuta
authors: Makoto
authors: M
authors: Kimura
mesh_terms: D000992:Antitoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019843:Archaeal Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D017353:Gene Deletion; D043902:Pyrococcus horikoshii / Q000235:genetics / Q000378:metabolism*; D014118:Toxins, Biological / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics
chemical_list: D000992:Antitoxins; D019843:Archaeal Proteins; D014118:Toxins, Biological