{"id":321,"date":"2023-03-15T16:16:16","date_gmt":"2023-03-15T16:16:16","guid":{"rendered":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/?post_type=chapter&p=321"},"modified":"2023-04-07T10:37:10","modified_gmt":"2023-04-07T10:37:10","slug":"321","status":"publish","type":"chapter","link":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/chapter\/321\/","title":{"raw":"Prokaryotic gene regulation- Trp Operon","rendered":"Prokaryotic gene regulation- Trp Operon"},"content":{"raw":"

The\u00a0trp<\/em>\u00a0Operon: A Repressor Operon<\/span><\/strong><\/h3>\r\n

Bacteria such as\u00a0<\/span>E. coli<\/em>\u00a0<\/span>need amino acids\u00a0 like tryptophan to survive, which they can ingest from the environment.<\/p>\r\n\u00a0<\/span>E. coli<\/em>\u00a0<\/span>can also synthesize tryptophan using enzymes that are encoded by five genes in the\u00a0tryptophan (trp<\/em>) operon<\/span><\/strong> .<\/span>\r\n\r\n <\/span>If tryptophan is available in the environment, then there is no necessity for\u00a0 \u00a0<\/span>E. coli<\/em>\u00a0<\/span>does\u00a0 to synthesize it and the\u00a0<\/span>trp<\/em>\u00a0<\/span>operon is switched off. However, when tryptophan availability is low,\u00a0 the operon is turned on, transcription is initiated, the genes are expressed, and tryptophan is synthesized.\r\n\r\nLike lac operon , trp operon also consists of structural genes and regulatory genes\r\n\r\nThe regulatory genes<\/strong> include\r\n\r\nP\/O genes<\/strong> :\u00a0 Promoter sequence and the operator sequence which is found in the promoter region.\r\n\r\ntrp L :<\/strong> Leader sequence : attenuator (A) sequence is found in the leader\r\n\r\nThe structural genes<\/strong> are\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
trp<\/em><\/strong>\u00a0Operon Gene<\/strong><\/td>\r\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Gene Function<\/strong><\/td>\r\n<\/tr>\r\n
<\/td>\r\n<\/td>\r\n<\/tr>\r\n
trp E<\/em><\/td>\r\nGene for anthranilate synthetase subunit<\/td>\r\n<\/tr>\r\n
trp<\/em>\u00a0D<\/em><\/td>\r\nGene for anthranilate synthetase subunit<\/td>\r\n<\/tr>\r\n
trp<\/em>\u00a0C<\/em><\/td>\r\nGene for glycerolphosphate synthetase<\/td>\r\n<\/tr>\r\n
trp B<\/em><\/td>\r\nGene for tryptophan synthetase subunit<\/td>\r\n<\/tr>\r\n
trp A<\/em><\/td>\r\nGene for tryptophan synthetase subunit<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nThe trp operon is a repressible systems because\u00a0 the binding of the effector molecule to the repressor greatly increases the affinity of repressor for the operator . The repressor binds to the operator\u00a0 and stops transcription. Thus<\/span> if tryptophan\u00a0 (effector) is\u00a0 available in the medium\u00a0 <\/span>\u00a0the repressors binds at the operator and repress the trp operon.<\/span>\r\n\r\n\"Tryptophan\r\n

Histidine-Trpoperon <\/a>by\u00a0Wikimedia Commons licensed under CC BY-SA 3.0<\/a><\/p>\r\n \r\n

Attenuation of the\u00a0trp<\/i>\u00a0Operon<\/h2>\r\n