Macromolecules IIMay 4, 2009

Jane Yu

Transfer-messenger RNA

Discovery of tmRNAa small, stable RNA

Ray and Apirion, 1979

Jain, et al. 1982

Where is tmRNA found?

• All sequenced eubacteria• Some rare mitochondrial

and plastidial genomes in simple eukaryotes such as diatoms.

• Some phage genomes• No nuclear genomes

What is tmRNA?mRNA-like and tRNA-like properties

Structure of tmRNA

Ribosomal RNA is normally recycled post-translation

tmRNA “rescues” ribosomes stalled during translation of mRNA lacking

stop codons.

A ribosome stuck with nonstop RNA

tmRNA “rescues” ribosomes stalled during translation of mRNA lacking

stop codons.

A sad ribosome stuck with nonstop RNA

tmRNA also:

1) mediates degradation of the aberrant mRNA

2) adds a degradation tag to the aberrant protein for directed proteolysis

Functions of tmRNA

The tmRNA/SmpB complex

Trans-translation

Role in human disease

Vital for normal growth in:

Mycobacterium pneumoniae

Neisseria gonorrhaeaeVital for pathogenesis in:Salmonella typhimurium (MP survival)Yersinia pseudotuberculosis (T3SS)