PubMed:6440121 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PubMed/sourceid/6440121","sourcedb":"PubMed","sourceid":"6440121","source_url":"http://www.ncbi.nlm.nih.gov/pubmed/6440121","text":"Partial methylation of two adjacent adenosines in ribosomes from Euglena gracilis chloroplasts suggests evolutionary loss of an intermediate stage in the methyl-transfer reaction.\nBacterial, cytoplasmic and organellar ribosomes from a wide phylogenetic spectrum of organisms have a characteristic m6(2)Am6(2)A structure near the 3' end of the RNA of the small ribosomal subunit (SSU). We have studied one of the few exceptions to this extremely conserved post-transcriptionally modified sequence, i.e. dimethylation of only one of the two A's in chloroplasts from Euglena gracilis. It was established that only the A closest to the 5' end is dimethylated, the other one being unmodified. The methylation reaction was studied in vitro using ribosomes from a kasugamycin resistant mutant (ksgA) of Escherichia coli and purified methyl-transferase. Using limited amounts of the methyl donor S-adenosylmethionine (SAM) a partial level of methylation (50% of control) was attained. It is shown that in this case the 3' proximal A is dimethylated while the other is not. This suggests that dimethylation takes place in two successive stages. Apparently in E. gracilis chloroplasts the first stage of methylation does not occur.","tracks":[{"project":"bionlp-st-epi-2011-training","denotations":[{"id":"T1","span":{"begin":787,"end":791},"obj":"Protein"}],"attributes":[{"subj":"T1","pred":"source","obj":"bionlp-st-epi-2011-training"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"bionlp-st-epi-2011-training","color":"#93ecb8","default":true}]}]}}