Structure probing of tmRNA in distinct stages of trans-translation

• Ribosomes stalled on problematic mRNAs in bacterial cells can be rescued by transfer-messenger RNA (tmRNA), its helperprotein (small protein B, SmpB), and elongation factor Tu (EF-Tu) through a mechanism called trans-translation. In this work weused lead(II) footprinting to probe the interactions of tmRNA with SmpB and other components of the translation machinery atdifferent steps of the trans-translation cycle. Ribosomes with a short nascent peptide stalled on a truncated mRNA were reactedwith Ala-tmRNA EF-Tu GTP, SmpB, and other translation components to initiate and execute trans-translation. Free tmRNA was                  d      dprobed with lead(II) acetate with and without SmpB, and ribosome bound tmRNA was probed in one of four different trans-translation states stabilized by antibiotic addition or selective exclusion of translation components. For comparison, we alsoanalyzed lead(II) cleavage patterns of tmRNA in vivo in a wild-type as well as in an SmpB-deficient Escherichia coli strain. Weobserved some specific cleavages/protections in tmRNA for the individual steps of trans-translation, but the overall tmRNAconformation appeared to be similar in the stages analyzed. Our findings suggest that, in vivo, a dominant fraction of tmRNA isin complex with SmpB and that, in vitro, SmpB remains tmRNA bound at the initial steps of trans-translation.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

tmRNA

SmpB

structural probing

lead(II)

trans-translation

Biology

Biologi

Publikations- och innehållstyp

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