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- Title
Co-evolution of multipartite interactions between an extended tmRNA tag and a robust Lon protease in Mycoplasma.
- Authors
Ge, Zhiyun; Karzai, A. Wali
- Abstract
Messenger RNAs that lack in-frame stop codons promote ribosome stalling and accumulation of aberrant and potentially harmful polypeptides. The SmpB-tmRNA quality control system has evolved to solve problems associated with non-stop mRNAs, by rescuing stalled ribosomes and directing the addition of a peptide tag to the C-termini of the associated proteins, marking them for proteolysis. In Escherichia coli, the ClpXP system is the major contributor to disposal of tmRNA-tagged proteins. We have shown that the AAA+ Lon protease can also degrade tmRNA-tagged proteins, but with much lower efficiency. Here, we present a unique case of enhanced recognition and degradation of an extended Mycoplasma pneumoniae ( MP) tmRNA tag by the MP-Lon protease. We demonstrate that MP-Lon can efficiently and selectively degrade MP-tmRNA-tagged proteins. Most significantly, our studies reveal that the larger (27 amino acids long) MP-tmRNA tag contains multiple discrete signalling motifs for efficient recognition and rapid degradation by Lon. We propose that higher-affinity multipartite interactions between MP-Lon and the extended MP-tmRNA tag have co-evolved from pre-existing weaker interactions, as exhibited by Lon in E. coli, to better fulfil the function of MP-Lon as the sole soluble cytoplasmic protease responsible for the degradation of tmRNA-tagged proteins.
- Subjects
MESSENGER RNA; RIBOSOMES; POLYPEPTIDES; PROTEINS; PROTEOLYSIS; MYCOPLASMA pneumoniae
- Publication
Molecular Microbiology, 2009, Vol 74, Issue 5, p1083
- ISSN
0950-382X
- Publication type
Article
- DOI
10.1111/j.1365-2958.2009.06923.x