title: Specific incorporation of selenium into lysine- and glutamate- accepting tRNAs from Escherichia coli.
abstract: Amino acid transfer nucleic acids (tRNAs) that contain selenium-modified bases are synthesized by Escherichia coli in the presence of low levels (0.1-0.5 microM) of [75Se]selenite or [75Se]selenate. The amount of selenium incorporated (1-2 g atoms/100 mol of tRNA) was unchanged by 10-20-fold variations in selenium or sulfate concentrations or by the addition of 1 mM cysteine, sulfide, or sulfite. Specific incorporation of selenium (as opposed to nonspecific substitution for sulfur) was further indicated by the different reversed phase chromatographic elution patterns of 35S- and 75Se-labeled tRNAs isolated from cells labeled with 35SO2-4 and 75SeO2-4. Also, E. coli mutants unable to synthesize an abundant sulfur-modified base, 4-thiouracil, nevertheless produced normal levels of selenium-modified tRNAs. Two different methods of distinguishing between aminoacylated and nonaminoacylated tRNA, one which examined mobility during reversed phase chromatography and another which employed anti-AMP antibodies, indicated that over 50% of the selenium-containing tRNA had lysine or glutamate acceptor activity.
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D009154:Mutation; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D011868:Radioisotopes; D012643:Selenium / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D012346:RNA, Transfer, Amino Acyl; D011868:Radioisotopes; D012643:Selenium