title: Tetrahydrofolate-dependent biosynthesis of ribothymidine in transfer ribonucleic acids of Gram-positive bacteria.
abstract: Trimethoprim, an inhibitor that prevents tetrahydrofolate-dependent transmethylation reactions inbacteria, was used in a comparative study to discriminate between two possible biosynthetic pathways, either the S-adenosylmethionine or the tetrahydrofolate-dependent formation of ribothymidine (rT) in transfer ribonucleic acids (tRNA's) of several strains of gram-positive and gram-negative microorganisms. rT-deficient tRNA's accumulate in trimethoprim-treated gram-positive Streptococcus faecium, Staphylococcus aureus, Corynebacterium bovis, Arthrobacter albidus, and all examined Bacillaceae, except Bacillus stearothermophilus. The rT-deficient rT-deficient tRNA's accept the methyl moiety from S-adenosylmethionine in vitro, with extracts from Escherichia coli (wild type) as a source of methylating enzymes; 90% of the incorporated methyl groups are present in rT. Trimethoprim does not inhibit the biosynthesis of rT in tRNA of gram-negative Enterobacteriaceae, Rhizobium lupini, and Pseudomonadaceae, suggesting that the rT-specific tRNA methyltransferases of these gram-negative strains use S-adenosylmethionine as coenzyme.
mesh_terms: D001173:Arthrobacter / Q000378:metabolism; D001407:Bacillus / Q000378:metabolism*; D003352:Corynebacterium / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D008745:Methylation; D012329:RNA, Bacterial / Q000096:biosynthesis*; D012343:RNA, Transfer / Q000096:biosynthesis*; D012263:Ribonucleosides / Q000096:biosynthesis*; D013210:Staphylococcus / Q000378:metabolism; D013291:Streptococcus / Q000378:metabolism; D013763:Tetrahydrofolates / Q000494:pharmacology*; D014295:Trimethoprim / Q000494:pharmacology; D014529:Uridine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D012359:tRNA Methyltransferases / Q000378:metabolism
chemical_list: D012329:RNA, Bacterial; D012263:Ribonucleosides; D013763:Tetrahydrofolates; C009182:ribothymidine; D012343:RNA, Transfer; D014295:Trimethoprim; D012359:tRNA Methyltransferases; D014529:Uridine