VapC20 of Mycobacterium tuberculosis cleaves the sarcin-ricin loop of 23S rRNA.
The highly persistent and often lethal human pathogen, Mycobacterium tuberculosis contains at least 88 toxin-antitoxin genes. More than half of these encode VapC PIN domain endoribonucleases that inhibit cell growth by unknown mechanisms. Here we show that VapC20 of M. tuberculosis inhibits translation by cleavage of the Sarcin-Ricin loop (SRL) of 23S ribosomal RNA at the same position where Sarcin and other eukaryotic ribotoxins cleave. Toxin-inhibited cells can be rescued by the expression of the antitoxin, thereby raising the possibility that vapC20 contributes to the extreme persistence exhibited by M. tuberculosis. VapC20 cleavage is inhibited by mutations in the SRL that flank the cleavage site but not by changes elsewhere in the loop. Disruption of the SRL stem abolishes cleavage; however, further mutations that restore the SRL stem structure restore cleavage, revealing that the structure rather than the exact sequence of the SRL is important for this activity.
Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle NE2 4HH, UK.
Kristoffer S
KS
Winther
Ditlev E
DE
Brodersen
Alistair K
AK
Brown
Kenn
K
Gerdes
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D004722:Endoribonucleases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D012338:RNA, Ribosomal, 23S / Q000737:chemistry / Q000378:metabolism*; D012276:Ricin / Q000737:chemistry / Q000378:metabolism*; D037521:Virulence Factors / Q000737:chemistry / Q000633:toxicity*
D001426:Bacterial Proteins; D005656:Fungal Proteins; D012338:RNA, Ribosomal, 23S; D037521:Virulence Factors; C014801:alpha-sarcin; D012276:Ricin; D004722:Endoribonucleases