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32 Cards in this Set
- Front
- Back
Enzyme encoded by lacZ gene |
Glucose and galactose products Enzyme cleaves broad range of galactosides |
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Structural genes of lac operon |
Encode for the primary structure of the enzymes/proteins lac Z, lac Y, and lac A |
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Lac I |
constitutive promoter and is expressed separately from the lac operon Encodes lac repressor - low level of expression |
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Holoenzyme |
RNA polymerase that can transcribe any gene that has a functional promoter |
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Repressors |
Regulatory proteins that decrease the level of transcripts for certain genes |
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Activators |
Proteins that increase transcription |
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Regulatory sequences |
Specific DNA regions to which regulatory proteins bind (kb) |
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Operator sites |
sequences recognized by regulators in bacteria |
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Eukaryotic Vs Prokaryotic |
E. genes are more often controlled by distal regulatory sequences |
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Locus control regions |
Found in more complex eukaryotes Enhancer and insulator elements
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DNA looping |
May bring the bound proteins to the promoter and encourage assembly of the transcription initiation complex |
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Regulatory proteins |
Have a DNA binding domain that recognizes a specific sequence Often modular Aid in oligomerization Activate or repress transcription Interact with other regulators |
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Allosteric effectors |
Small molecules that can bind directly to the regulatory proteins and change their conformation Estrogen |
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Helix turn helix |
common and found in many protein folds. First helix and recognition helix fits in the major groove Many are dimers with the recognition helices spaced 3.4 nm apart to fit neighboring grooves |
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Recognition helices |
In helix turn helix proteins read the DNA sequence through interactions with the base pairs Homeodomain |
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Homeodomain |
is a monomeric helix turn helix |
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Zinc finger |
Prominent part of many DNA binding folds Interacts with the two cysteines and two histidines Insert its alpha helix into the minor groove Most common DNA binding domains in the human genome |
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Coiled-coils |
alpha helices that wind around each other form part of some DNA binding domains |
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Basic region leucine zipper proteins |
have long alpha helices of about 60 amino acids
The two helices have hydrophobic leucing residues on the surfaces that "zip" together |
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Basic region helix loop helix proteins |
Have a coiled coil and a helix that fits in the major groove Have four helices joined by a loop. The region where the four helices interact is the Four Helix Bundle |
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Immunoglobulins |
Made of beta sheets and connecting loops |
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Trp repressor |
Helix turn helix protein Depends on the level of tryptophan in the cell When tryptophan levels are high, binds to operator and blocks RNA polymerase from binding |
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RNA polymerase + promoter |
Activate transcription |
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Catabolite activator protein |
Activates more than 100 E. coli promoters when carbon sources are low |
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Glucose depletion |
Increases cAMP levels - this binds to CAP and increases its binding to DNA |
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CAP |
enhances RNA polymerase by binding to the CTD Class I: binds upstream of promoter Class II: the CAP binding site overlaps the RNA polymerase binding site |
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CAP and Lac I |
Regulate the lac operon |
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Lac operon |
Responds to low glucose levels in the cell by allowing it to metabolize lactose instead if present |
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In low glucose, lactose available |
CAP binds to the CAP operator, enhancing transcription STRONGLY ON |
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In high glucose, lactose available |
Cap does not bind to the CAP operator, the lac repressor is not bound, WEAK transcription |
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NtrC |
Activates genes that are important for nitrogen metabolism Binds at enhancer elements and activates transcription when phosphorylated |
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Oligomerization |
Stimulates its rate of ATP hydrolysis, which helps promote formation of the open complex |