title: Magic spot metabolism in an Escherichia coli mutant temperature sensitive in elongation factor Ts.
abstract: A temperature-sensitive mutant of Escherichia coli HAK88 which has been shown to have a lesion in elongation factor Ts (EFTs) was studied with repsect to its metabolism of guanosine 5'-diphosphate, 2'(3')-diphosphate (ppGpp) and the associated failure of ribosomal ribonucleic acid (rRNA) accumulation at the nonpermissive temperature. Results reported here show that (i) when EFTs is nonfunctional, a full complement of charged transfer RNA (tRNA) cannot prevent accumulation of ppGpp (magic spot) and the stringent failure of rRNA accumulation; (ii) chloramphenicol prevents magic spot (MS) formation and the stringent response not by increasing the percentage of charged tRNA, but possibly by somehow interfering directly with the synthesis of MS; and (iii) tetracycline can lead to MS disappearance without resumption of RNA synthesis. Thus, the absence of MS and the presence of a functional RNA polymerase and charged tRNA are not sufficient to support rRNA accumulation in vivo. An additional element in the regulatory system is suggested.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D002250:Carbon Radioisotopes; D002701:Chloramphenicol / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D009154:Mutation; D010445:Peptide Elongation Factors / Q000096:biosynthesis*; D010761:Phosphorus Radioisotopes; D012329:RNA, Bacterial / Q000096:biosynthesis; D012335:RNA, Ribosomal / Q000096:biosynthesis; D012343:RNA, Transfer / Q000378:metabolism; D013696:Temperature; D013752:Tetracycline / Q000494:pharmacology; D014316:Tritium; D014498:Uracil / Q000378:metabolism
chemical_list: D000596:Amino Acids; D002250:Carbon Radioisotopes; D006150:Guanine Nucleotides; D010445:Peptide Elongation Factors; D010761:Phosphorus Radioisotopes; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; D014316:Tritium; D014498:Uracil; D002701:Chloramphenicol; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D013752:Tetracycline