Small protein B (SmpB) is a component of the trans-translation system in prokaryotes for releasing stalled ribosome from damaged messenger RNAs
Small protein B (SmpB) is a component of the trans-translation system in prokaryotes for releasing stalled ribosome from damaged messenger RNAs and targeting incompletely synthesized protein fragments for degradation. Trans-translation system is composed of a ribonucleoprotein complex of tmRNA, a specialized RNA with properties of both tRNA and mRNA, and SmpB. SmpB is highly conserved and present in all bacterial kingdoms and is also found in some chloroplasts and mitochondria. This is suggesting Trans-translation arose early in bacterial evolution and its mechanism is a quality control for protein synthesis in spite of challenges such as transcription errors, mRNA damage, and translation frame shifting. SmpB deletion results in phage development defects phenotype and absence of tagged proteins translated from defective mRNAs.
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