Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0039483 (giant cell arteritis)
 3,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently reported that the gene for chloroplast tRNA(Cys)(GCA) is a pseudogene in the plastid DNA of Epifagus virginiana, a non-photosynthetic parasitic flowering plant in the family Orobanchaceae. Since this is the only tRNA(Cys) gene in the plastid genome, and since Epifagus appears to possess a functional plastid translational apparatus, it seems probable that nuclear-encoded tRNAs are imported into plastids to effect translation. In this study we have surveyed species closely related to Epifagus to establish how widespread the loss of this tRNA gene has been. We find that Conopholis americana, another non-photosynthetic parasite, lacks the gene altogether, but that seven closely-related photosynthetic plants (both parasitic and free-living) maintain an intact chloroplast tRNA(Cys) gene. Thus, the tRNA(Cys) gene appears to have become non-functional at the same time that photosynthetic ability was lost. This may be because the levels of putatively imported tRNAs are sufficient to meet the demands of plastid gene expression under nonphotosynthetic conditions only.
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PMID:Lack of a functional plastid tRNA(Cys) gene is associated with loss of photosynthesis in a lineage of parasitic plants. 172 64

The trans-translation system in bacteria promotes recycling of stalled ribosomes and targets incomplete peptides for proteolysis. In Escherichia coli, loss of trans-translation function has little effect on growth under normal laboratory conditions. Among the subtle phenotypes of tmRNA-deficient mutants is the inability to plate certain lambda imm(P22) phages. This phenotype is dependent on the ribosome recycling functions of the trans-translation system but is independent of its proteolysis-targeting activity. The experiments described here show that translation of the first (resume) codon of the tmRNA open reading frame by a tRNA is both necessary and sufficient for ribosome recycling. While a variety of sense codons can replace the naturally-occurring GCA alanine codon as the resume codon, both AAA and AAG lysine codons are non-functional resume codons. These results suggest that the main function of tmRNA in releasing stalled ribosomes is to supply a stop codon and so facilitate termination and subsequent ribosome recycling.
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PMID:Minimal translation of the tmRNA tag-coding region is required for ribosome release. 1741 10