title: Micro-analysis of pure deoxyribonucleic acid-dependent ribonucleic acid polymerase from Escherichia coli. Action of heparin and rifampicin on structure and function.
abstract: By using micro disc electrophoresis and micro-diffusion techniques, the interaction of pure DNA-dependent RNA polymerase (EC 2.7.7.6) from Escherichia coli with the template, the substrates and the inhibitors heparin and rifampicin was investigated. The following findings were obtained: (1) heparin converts the 24S and 18S particles of the polymerase into the 13S form; (2) heparin inhibits RNA synthesis by dissociating the enzyme-template complex; (3) rifampicin does not affect the attachment of heparin to the enzyme; (4) the substrates ATP and UTP are bound by enzyme loaded with rifampicin; (5) rifampicin is bound by an enzyme-template complex to the same extent as by an RNA-synthesizing enzyme-template complex. From this it is concluded that the mechanism of the inhibition of RNA synthesis by rifampicin is radically different from that by heparin. As a working hypothesis to explain the inhibitory mechanism of rifampicin, it is assumed that it becomes very firmly attached to a position close to the synthesizing site and only blocks this when no synthesis is in progress.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001345:Autoradiography; D004589:Electrophoresis, Disc; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D006493:Heparin / Q000494:pharmacology*; D008832:Microchemistry; D011485:Protein Binding; D012316:RNA Nucleotidyltransferases / Q000032:analysis* / Q000037:antagonists & inhibitors; D012293:Rifampin / Q000494:pharmacology*; D013460:Sulfur Isotopes; D014316:Tritium; D014500:Uracil Nucleotides / Q000378:metabolism
chemical_list: D013460:Sulfur Isotopes; D014500:Uracil Nucleotides; D014316:Tritium; D006493:Heparin; D012316:RNA Nucleotidyltransferases; D000251:Adenosine Triphosphatases; D012293:Rifampin