title: Interaction between the first enzyme for histidine biosynthesis and histidyl transfer ribonucleic acid.
abstract: Previous studies suggested that phosphoribosyltransferase, which catalyzes the first step of the pathway for histidine biosynthesis in Salmonella typhimurium and which is sensitive to inhibition by histidine, plays a role in repression of the histidine operon. Recently, we showed that the enzyme has a high affinity for histidyl transfer ribonucleic acid (His-tRNA), which is known to participate in the repression process. In the present study, we have investigated further the interaction between the enzyme and His-tRNA. We found that His-tRNA binds at a site on phosphoribosyltransferase distinct from the catalytic site and the histidine-sensitive site; that the substrates of the enzyme inhibit the binding of His-tRNA, whereas histidine does not do so; that, once a complex has been formed between phosphoribosyltransferase and His-tRNA, the substrates of the enzyme decrease the stability of the complex, whereas histidine is without effect; and that purified phosphoribosyltransferase which has a defect in its inhibition by histidine (produced by mutation) displays an altered ability to bind His-tRNA, a finding which may be a reflection of the fact that mutants producing such a defective enzyme display an alteration of the repression process.
mesh_terms: D000179:Acrylates; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001665:Binding Sites; D004586:Electrophoresis; D004794:Enzyme Repression; D005374:Filtration; D005782:Gels; D005827:Genetics, Microbial; D006639:Histidine / Q000096:biosynthesis*; D006358:Hot Temperature; D009154:Mutation; D009578:Nitrobenzenes / Q000494:pharmacology; D012343:RNA, Transfer / Q000302:isolation & purification / Q000378:metabolism*; D012265:Ribonucleotides / Q000494:pharmacology; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000378:metabolism; D014166:Transferases / Q000302:isolation & purification / Q000378:metabolism*; D014316:Tritium
chemical_list: D000179:Acrylates; D005782:Gels; D009578:Nitrobenzenes; D012265:Ribonucleotides; D014316:Tritium; D006639:Histidine; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D014166:Transferases