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93 Cards in this Set
- Front
- Back
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For regulated cells, what are the three ways this is done?
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-activity
-amount -location |
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What are unregulated cells (processes?) called?
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-constitutive
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What are the two places enzyme synthesis can be regulated?
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-at translation
-at transcription |
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What is allosteric inhibition?
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-the inhibitor (effector) non-covalently binds to allosteric site (non-active) and causing conformational change adn inhibiition
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What is feedback inhibition?
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-inhibitor is end product of reaction
-usually inhibits first enzyme (rate-limiting) in pathway -commonly used in branched pathways |
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When is enzyme activity completely inhibited?
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-when ALL isozymes are inhibited
*different end products can inhibit different isozymes that catalyze the same reaction |
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What are isozymes?
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-enzymes that differ in amino acid sequence but catalyze the same chemical reaction
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What are 5 types of Post-translational modifications?
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-adenylation
-protein processing -protein splicing -phosphorylation -ubiquitination |
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What is the definition of post-translational modifications?
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-multiple mechanisms to alter enzyme activity
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What are the two types of phosphorylated proteins?
What else can be regulated with phosphorylated proteins? |
-active
-inactive +kinases and phosphatases (also by dephosphorylation) |
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What is adenylation?
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-covalent attachment of AMP molecules
-glutamine synthetase |
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What is protein processing?
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-removal of amino acids
-cross linking of polypeptides |
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What is protein splicing?
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-similar to RNA splicing
-removal of internal amino acids |
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What is phosphorylation?
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-addition of phosphate froup to ser, thr, or tyr residue
-most prevalent form of modification in eukaryotes |
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What is ubiquitanation?
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-addition of ubiquitin polypeptide
-leads to proteolysis |
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How can synthesis of enyzmes respond to environmental factors?
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-increased or decreased (induced or repressed)
-level of transcription or coupled transcription/translation |
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What is enzyme induction?
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-catabolic pathways
-enzymes needed to break down a molecule are only synthesized when molecule is present -molecule (or derivative) acts as an inducer; induction can be under negative and/or positive control |
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What is enzyme repression?
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-anabolic pathways
-enzymes needed to synthesize a molecule are not made if molecule is present -end-product acts as co-repressor -repression is only under negative control |
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What is the operon?
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-multiple genes that are coordinately regulated
-contained in a single polycistronic mRNA -inducible or repressible |
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What is the regulon?
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-multiple genes that are coordinately regulated
-different mRNA's |
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Describe inducible operons?
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-catabolic pathways
-regulates presence of substrate of pathways -lac operon |
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Describe repressible operons?
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-anabolic pathways
-presence of product -trp operon |
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What are proteins that negatively regulate transcription?
How about positive control? |
-repressors
-activators |
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How do repressors regulate transcription?
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-negatively control transcription
-bind to DNA sequences (operators) and inhibit RNA polymerase -inducers and co-repressors enter the cell and bind to repressor -affect ability to bind to DNA |
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What do inducers do?
Co-repressors? |
-dissociate repressor-operator binding
-induce repressor-operator binding |
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Can induction and repression both be negatively controlled by repressors?
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-yes
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How do activators work?
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-proteins that induce transcription
-usually interact with RNA polymerase and stabilize transcription initiation complex -can work with repressors or separately -most common form of regulation in eukaryotes -interactions with RNA polymerase can lead to DNA bending |
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What are two types of DNA-binding proteins?
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-repressors and activators
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Describe the types of DNA-binding proteins?
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-sequence specific
-helix turn helix -zinc fingers -leucine zipper |
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How are DNA-binding proteins sequence-specific?
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-specific amino acids in protein recognize specific bases in DNA
-usually in the major groove |
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Describe DNA binding sites?
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-inverted repeats
-palindromic sequences -multiple structural motifs used by DNA binding proteins |
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What uses helix turn helix DNA binding proteins?
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-prokaryotic repressors
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What uses zinc-fingers in DNA-binding proteins?
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-eukaryotic regulators
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What uses leucine zipper DNA-binding proteins?
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-eukaryotic regulators
-holds helices together |
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What is global regulation?
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-catabolite repression
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What is a regulon?
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-multiple genes coordinately regulated by same environmental signal
-many examples-nutrient utilization, stress responses |
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What is the glucose effect?
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-when glucose is present, E. coli will NOT use other sugars until the glucose is used up
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What affect does glucose have on cAMP and transcription?
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-glucose present: cAMP levels are low and transcription is not induced
-glucaose absent: cAMP levels are high and CAP-dependent transcription is induced |
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Describe glucose effect
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-catabolite repression
-occurs through transcriptional induction -catabolite activator protein (CAP) binds to cAMP molecule, then interacts with RNA polymerase |
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What is the only thing that can use coupled transcription-translation?
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-bacteria using attenuation
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Describe attenuation.
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-translation of short loader peptide affects transcription termination
-only found in prokaryotes -primarily seen in anabolic pathways such as amino acid biosynthesis |
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What does the rate of translation determine?
What does this affect? |
-availability of charged tRNA molecules
-this affects sexondary structure of mRNA formed |
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In attenuation, how is transcription affected by tyrptophan?
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-terminated with excess tryptophan
-transcription not terminated if tryptophan starved |
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What is the two-component regulatory system used for?
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-signal transduction
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What is signal transduction?
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-signal from environmental factors are transduced to transcriptional machinery via signaling molecules
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What is the two-component system?
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-sensor kinase and response regulator
-phosphatase inactivates regulator when signal decreases |
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How does kinase phosphorylates regulator work?
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-it recieves a response from environmental signal and acts either as a repressor or activator of transcription
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What are some examples of two-component systems and which bacteria uses them?
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-nitorgen fixation by Klebsiella
-sporulation by Bacillus -osmolarity by E. coli (has 50 two-component systems) |
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Do east and other eukaryotic microbes have two-component systems?
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-no, but they have similar two-component systems and other signal transduction systems
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What are the 4 important viruses studied for replication in class?
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-HIV
-Poliovirus -Herpes Simplex Virus 1 -Influenza Virus |
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What are three types of virus replication?
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-direct penetration
-membrane fusion -phagocytosis |
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What viruses use direct penetration and what happens here?
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-non-enveloped (naked) viruses such as poliovirus
-genome is inserted but capsid remains outside cell |
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What viruses use membrane fusion and what happens here?
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-enveloped viruses such measles and mumps
-viral envelope fuses with plasma membrane |
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What viruses use phagocytosis?
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-enveloped viruses such as herpesvirus
-entire virion is engulfed by phagocytosis -viral envelope is removed inside cell by uncoating enzymes |
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What are viral receptors for?
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-function in cell to cell or cell to environmentcommunication
-can have multiple other functions -only cells that contain receptor are infected by virus |
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What are the different types of receptor classes?
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-cell adhesion and cell-cell contact proteins
-complement control protein superfamily -other proteins -extracellular matrix components and sugar derivatives |
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What is the cell structure and receptor class of HIV family?
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-cell adhesion and cell to cell contact proteins
-CXCR4 (TM7 family) |
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What is the cell structure and receptor class of Poliovirus?
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-other protiens
-PVR and related proteins HveB and HveC (ig superfamily) |
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What is the cell structure and receptor class of Influenza?
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-extracellular matrix components and sugar derivatives
-sialic acid |
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How do non-enveloped viruses enter into a bacteria?
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-virion binds to cell receptor Pvr
-capsid proteins form a pore for the release of RNA into cells *RNA may enter at binding site or after pore separates membrane and enters cell |
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What mediates fusion and entry of virion RNA into a bacteria for membrane fusion?
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-viral envelope glycoproteins
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How does membrane fusion work?
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-once bound to the receptor, the viral genome is delivered across the cellular lipid bilayer
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What are some viral envelope glycoproteins?
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-CD4 binding
-Exposure of CoR binding site -Triple-stranded coiled-coil -Coreceptor binding -6-helix bundle |
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What is virus production?
What does this depend on? |
-combination of replication of genome and virus assembly
-depends on nucleic acid |
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What must be considered during animal virus replication?
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-how mRNA is synthesized
*only +ssRNA can act as an mRNA for translation, -ssRNA must be transcribed into +ssRNA -what serves as a template for nucleic acid replication |
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What is the genome, how is it synthesized, and what molecule is the template for genome replication in Herpes virus (2)?
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*dsDNA
*By RNA polymerase (in nucleus or cytoplasm of cell) *each strand of DNA serves as template for its complement (except hepatitis B which synthesizes RNA to act as the template for new DNA) *ssDNA by RNA polymerase in nucleus of cell using complementary strand of DNA is synthesized to act as template |
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What is the genome, how is it synthesized, and what molecule is the template for genome replication in Polio virus?
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*+ssRNA
*genome acts as mRNA *-RNA is synthesized to act as template |
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What is the genome, how is it synthesized, and what molecule is the template for genome replication in HIV?
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*+ssRNA (retroviridae)
*DNA is synthesized from RNA by reverse transcriptase, mRNA is transcribed from DNA by RNA polymerase *DNA |
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What is the genome, how is it synthesized, and what molecule is the template for genome replication in Influenza virus?
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*-ssRNA
*by RNA dependent RNA transcriptase *+RNA (mRNA) |
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What is the genome, how is it synthesized, and what molecule is the template for genome replication in Rotavirus?
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*dsRNA
*Positive stand of genome acts as mRNA *each strand of genome acts as template for its complement |
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Describe retrovirus HIV genome.
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-genome reverse transcribed by viral RNA-dependent DNA polymerase called 'reverse transcriptase'
-(+ssRNA to DNA to +ssRNA) |
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Describe the replication of Retrovirus-HIV.
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-DNA is integrated into the host cell chromosomes
-DNA is then transcribed by host RNA polymerases to make more +ssRNA -this +ssRNA then acts as mRNA for synthesis of viral proteins and genome for new viruses |
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Describe poliovirus genome.
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-genome is transcribed by viral RNA-dependent RNA polymerase to make -ssRNA and then more +ssRNA
- (+ssRNA to -ssRNA to +ssRNA) |
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Describe the replication of poliovirus.
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-replication occurs in membrane spherules (genome NOT integrated into host genome in nucleus)
-this +ssRNA (from the -ssRNA from polymerase) then acts as mRNA for synthesis of viral proteins and genome for new viruses |
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Describe Herpes simplex virus 1's genome.
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-genome is replicated by DNA polymerase in nucleus
-DNA to DNA |
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Describe how Herpes Simplex Virus 1 is replicated.
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-DNA transcribed by host RNA polymerases to make mRNA
-mRNA then directs synthesis of viral proteins and capsids are assemble in nucleus *DNA NOT integegrated into the host cell chromosomes |
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Describe influeza virus' genome replication.
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-genome is replicated by RNA-dependent RNA polymerase (RNA transcriptase) in nucleus
-(-ssRNA to +ssRNA to -ssRNA) |
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How does the influenza virus replicate?
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-the +ssRNA acts as mRNA for synthesis of viral proteins and acts as a template for synthesis of -ssRNA genome for new viruses
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Where are most DNA virions assembled and released from?
Where are most RNA virions developed? |
-from the nucleus into cytosol
-solely in cytoplasm |
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What affects the number of viruses produced and released?
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-type of virus
-size of virus -initial health of host cell *how immune system deals with infection |
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How are naked viruses released from cell?
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-released through lysis and death of host cell
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How are enveloped viruses released from cell?
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-released by budding; acquires envelope this way
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What are the production steps in assembly and release of viruses?
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-transcription, translation, intracellular transport, encapsidation of genomic RNA, budding
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How much surface area of cell membranes are exchanged each hour?
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-50% of surface area
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How do viral components travel?
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-travel with membranes through the secretory pathway (and out of cell eventually)
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What are some potential consequences of integration of viral genome?
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-deregulation of nearby cancer genes
-activation of oncogene -suppression of tumor suppressor gene |
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What are some consequences of viral infection?
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-malignancy
-lysis of "host" cell -persistent infection -latent infection |
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What is latent infection?
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-no viral expression for extended time
-can reactivate and lead to cell lysis -ex: chickenpox, herpes virus |
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What is cancer in terms of replication?
What percent of cancers are virally induced and give some examples. |
-uncontrolled cell division
-mass of neoplastic cells is a tumor -15%: Burkitts lymphoma, Hodgkins disease, Kaposi's sarcoma, cervical cancer |
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How does malignancy occur in viral infection?
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-adsorption
-penetration -tumor cell division (transformation of normal cells to tumor cells) |
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How does lysis of "host" cell result from viral infection?
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-adsorption
-penetration -multiplication -death of cell and release of virus |
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How does persistent infection work in viral infection?
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-adsorption
-penetration -slow release of virus without cell death |
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How does latent infection work in viral infection?
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-adsorption
-penetration -virus present but not causing harm to cell; later emerges in lytic infection |
