Lect25_regulation2

Lect25_regulation2 - Regulatory proteins can block or...

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1 Regulation of Gene Expression -- 2 Chapter 17 Regulatory proteins can block or attract RNA polymerase • Depending where a regulatory protein binds to the DNA, it can act to block RNA polymerase (and thus turn off genes; negative control ) • Or, it can help attract RNA polymerase to the promoter (and thus increase or enhance transcription of genes; positive control ) Activator Protein Repressor Protein Promoter DNA-binding Sequence that attracts Repressor ( Operator) Enzyme 3 of pathway Enzyme 1 of pathway Enzyme 2 of pathway Energy-shortage signal Substrate of pathway (lactose molecule) DNA-binding Sequence that attracts Activator DNA RNA polymerase Organize the components to perform the following program: If lactose is present, then make lactose-burning enzymes promoter Enzyme 1 Activator Protein Repressor Protein DNA-binding Sequence that attracts Repressor (Operator) Energy-shortage signal Substrate of pathway (fuel molecule) DNA-binding Sequence that attracts Activator RNA polymerase Enzyme 2 Enzyme 3 Organize genes into an operon … promoter Enzyme 1 Activator Protein Repressor Protein DNA-binding Sequence that attracts Repressor (Operator) Energy-shortage signal Substrate of pathway (lactose molecule) DNA-binding Sequence that attracts Activator RNA polymerase Enzyme 2 Enzyme 3 Decide how the if / then statement will be performed by the regulatory protein Organize the components to perform the following: If lactose is present, then make enzymes R operator promoter Enzyme 1 Activator Protein Energy-shortage signal Substrate of pathway (lactose molecule) DNA-binding Sequence that attracts Activator RNA polymerase Enzyme 2 Enzyme 3 Decide how the if / then statement will be performed by the regulatory protein Option 1: Repressor binds to operator R Repressor active when first made Repressor allosterically inactivated by lactose Organize the components to perform the following: If fuel (lactose) is present, then make enzymes
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2 A A promoter Enzyme 1 Energy-shortage signal Binding Seq RNA Enzyme 2 Enzyme 3 Decide how the if / then statement will be performed by the regulatory protein Option 2: Activator binds near promoter R Organize the components to perform the following: If fuel (lactose) is present, then make enzymes Activator inactive when first made Activator allosterically activated by lactose A The lac operon: regulated synthesis of inducible enzymes DNA mRNA Protein Active repressor RNA polymerase No RNA made lacZ lacl Regulatory gene Operator Promoter Lactose absent, repressor active, operon off. The lac repressor is innately active, and in the absence of lactose it switches off the operon by binding to the operator. (a) 5 3 mRNA 5' DNA mRNA Protein Al olactose (inducer) Inactive repressor lacl lacz lacY lacA RNA polymerase Permease Transacetylase β -Galactosidase 5 3 (b) Lactose present, repressor inactive, operon on. Al olactose, an isomer of lactose, derepresses the operon by inactivating the repressor. In this way, the enzymes for lactose utilization are induced.
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This note was uploaded on 03/08/2011 for the course BIS 2A taught by Professor Grossberg during the Fall '08 term at UC Davis.

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Lect25_regulation2 - Regulatory proteins can block or...

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