microbio Flashcards
(124 cards)
Some proteins are needed under all growth conditions
Proteins that are always being expressed are ____________
constitutive
Cells use two approaches to regulate protein function
Control the _______ of a protein
Control the ________of a protein
-amount
-activity
Primary form of regulation in Bacteria and Archaea
Transcriptional control
Small molecules influence the binding of _________ _______ to DNA
-Turns transcription on or off
Regulatory Proteins
Bacterial gene arrangement differs from eukaryotes.
-Lack _______
Can be arranged in operons:
two or more genes transcribed under the control of a _________region (single regulatory site) located upstream of where R N A polymerase initiates transcription
-introns
-promoters
Bacterial promoters characterized by distinct nucleotide sequences recognized and bound by ____-binding proteins
-Allows _____ polymerase to bind, transcription to occur
-DNA
-RNA
DNA-Binding Proteins
Interaction of Proteins with Nucleic Acids
Small molecules influence the binding of _________ ________ to DNA
-turns transcription up or down
may be _________-specific or ___________
-regulatory proteins
-squence
-nonspecific
Major ________ of DNA is the main site of protein binding
groove
DNA Binding Proteins
_________ ________frequently are specific binding sites for regulatory proteins.
Homodimeric proteins: proteins composed of two identical _____________
Each __________ has a _______ that binds to one inverted repeat.
Domain: region of a polypeptide with specific structure and function
-Inverted repeats
-polypeptide
-polypeptide
-domain
region of a polypeptide with specific structure and function
domain
Structure of DNA-Binding Proteins
helix-turn-helix
two α-helices connected by a short “turn” sequence
first helix the ________ helix
interacts specifically with ____
second helix the stabilizing helix
interacts with first helix through______________ interactions
-recognition
-DNA
-stabilizing
-hydrophobic
Many different DNA-binding proteins from Bacteria contain ____-____-_____
____and ___ repressors of E. coli
-helix-turn-helix
- lac
-trp
Structure of DNA-Binding Proteins
Eukaryotic regulatory protein structure that binds a zinc ion
Zinc finger domains
Structure of DNA-Binding Proteins
-Contains regularly spaced leucine residues
-Function to hold two recognition helices in the correct orientation
Leucine zipper domain
DNA Binding Proteins
Multiple outcomes after DNA binding are possible.
DNA-binding protein may catalyze a specific reaction on the DNA molecule (e.g., transcription by ___ polymerase)
The binding event can block transcription - ________ regulation
The binding event can activate transcription ________ regulation
-RNA
-negative
-positive
Proteins that control the rate of transcription by binding to specific DNA
Transcription factors
-turns on transcription
-Binds DNA and recruits RNA polymerase or sigma factor to promoter region
Activator protein
-turns off expression
-Binds operator region of DNA downstream of promoter
Repressor protein
_________ _______: Conformation altered when effector molecule binds
-Since transcription factors are allosteric, conformational change determines whether transcription factor can bind _____
-Allosteric proteins
-DNA
Transcription factors
Inducers turn ___ transcription, corepressors turn ____ transcription
-on
-off
Repression and Activation
:preventing the synthesis of an enzyme unless product is absent from culture medium; excess of product decreases enzyme synthesis
Enzyme repression
Enzyme repression
-Specific effect (synthesis of all other enzymes continues normally)
-Widespread as control for production of _____ _____ and nucleotide precursors
-Usually, final product of a biosynthetic pathway is the ___________ effector molecule
- Typically affects biosynthetic/anabolic enzymes
-amino acid
-corepressor
Repression and Activation
Enzyme induction:
-opposite of ___________
-production of an enzyme in response to presence of __________
-typically affects degradative/catabolic enzymes (e.g., ____ operon)
-ensures enzymes are ____________ only when needed
-repression
- substrate
-lac
-synthesized
Mechanisms of Repression and Derepression
Repressors turn off ___________
Corepressors only bind ____ in presence of its ________.
Example: Arginine becomes ___________when plentiful
Binds _______ repressor (Arg R)
Results in _______ change and ________ binding
Since arg mRNA is ___________, all peptides encoded are repressed
-transcription
-DNA,
-effector
-corepressor
-arginine
-allosteric
-operator
-polycistronic