A previously uncharacterized role for small protein B (SmpB) in transfer messenger RNA-mediated trans-translation.
SsrA is a versatile RNA molecule found in all bacteria that functions as both a tRNA and an mRNA. SsrA rescues ribosomes stalled on damaged mRNAs and directs the tagging and degradation of their aberrant protein products. Small protein B (SmpB) is required for all known activities of SsrA. The two known functions of SmpB are binding SsrA RNA and promoting stable association of the SmpB.SsrA complex with 70S ribosomes. Using mutational analysis and biochemical experiments, we have discovered a previously uncharacterized SmpB function. This function is required for a step in the tagging process downstream of SsrA binding and ribosome association but before transpeptidation of the SsrA-linked alanine and establishment of the SsrA reading frame. Our results clearly demonstrate that residues in the C-terminal tail of SmpB confer a hitherto unrevealed function that is essential for trans-translation. Based on these results, we propose that upon binding stalled ribosomes, the unstructured C-terminal tail of SmpB acquires contacts that are critical for productive accommodation of SsrA into the ribosomal A site.
Sundermeier
Thomas R
TR
Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA.
Dulebohn
Daniel P
DP
Cho
Hye Jin
HJ
Karzai
A Wali
AW
D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D016296:Mutagenesis; D010641:Phenotype; D011485:Protein Binding; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D012343:RNA, Transfer / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D017384:Sequence Deletion
D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C430328:small protein B; C096222:tmRNA; D012343:RNA, Transfer