Characterization of ChpBK, an mRNA interferase from Escherichia coli.
Escherichia coli contains a number of antitoxin-toxin modules on its chromosome, which are responsible for cell growth arrest and possible cell death. ChpBK is a toxin encoded by the ChpBIK antitoxin-toxin module. This module consists of a pair of genes, chpBI and chpBK encoding antitoxin ChpBI and toxin ChpBK, respectively. ChpBK consists of 116 amino acid residues, and its sequence shows 35% identity and 52% similarity to MazF, another E. coli toxin. MazF has been shown to be a sequence-specific (ACA) endoribonuclease that cleaves cellular mRNAs and effectively blocks protein synthesis and is thus termed as an mRNA interferase. Here we demonstrate that ChpBK is another mRNA interferase in E. coli whose induction effectively blocks cell growth in a manner similar to that of MazF. The protein synthesis as judged by incorporation of [35S]methionine was, however, reduced by only 60% upon ChpBK induction. We demonstrate that ChpBK is a new sequence-specific endoribonuclease that cleaves mRNAs both in vivo and in vitro at the 5'-or3'-side of the A residue in ACY sequences (Y is U, A, or G). The ChpBK cleavage of a synthetic RNA substrate generated a 2',3'-cyclic phosphate group at the 3'-end of the 5'-end product and a 5'-OH group at the 5'-end of the 3'-end product in a manner identical to that of MazF.
Zhang
Yonglong
Y
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA.
Zhu
Ling
L
Zhang
Junjie
J
Inouye
Masayori
M
D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000737:chemistry*; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004722:Endoribonucleases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D013997:Time Factors
D001427:Bacterial Toxins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C422955:MazF protein, E coli; D012333:RNA, Messenger; D012313:RNA; D004722:Endoribonucleases; C503487:ChpBK protein, E coli