Biochemistry 2280A Lecture Notes - Lecture 24: Nucleosome, Chromatin, Catabolite Repression
12 Dec 2016
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Topic 22 continued: trp operon = negative regulation of e. coli. When there"s a lot of tryptophan in the cellular environment. When there"s a little tryptophan in the cellular environment. D. unsure: trp operon is only expressed when there"s little to no tryptophan in the cellular environment. If the bacteria realizes there"s no tryptophan in the environment wants to express the trp operon and turn it on. Trp promoter has -10 and -35 sequence like most bacterial promoter. Between -10 and -35, there"s a special sequence called the trp operator, which binds a protein called the trp repressor (dna-protein interaction) When tryptophan concentration is high, the trp repressor binds to amino acid tryptophan trp repressor tryptophan complex binds to dna. When trp repressor complex is bound blocks rna polymerase from recognizing the -10 and -35. Only the complex has high affinity to the operator sequence! Trp repressor on its own has low affinity to operator sequence.
