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Microbiology > Lecture 7 > Flashcards

Lecture 7 Flashcards

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1
Q

True or False: Translation is usually the last step for producing a functional molecule.

A

False

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2
Q

What structures of a protein are modified after it has been assembled?

A

Primary, Secondary, and Tertiary

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3
Q

What does a healthy cell do to dysfunctional proteins?

A

It damages and degrades proteins that are not functional

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4
Q

What are primary protein chains composed of?

A

Amino acids

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5
Q

What structures can chains of amino acids fold into?

A

secondary (alpha helix or beta sheet) and tertiary structures

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6
Q

What do folded tertiary structures assemble into?

A

Quaternary structures

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7
Q

What happens when the N-formyl group is removed by
methionine deformylase?

A

can escape
immunorecognition

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8
Q

What occurs with the addition of phosphoryl or
methyl groups?

A

can change the
activity of signal transduction

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9
Q

What two substances can regulate protein activity?

A

Adenylylation and acetylation

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10
Q

What can be attached to proteins?

A

Lipids and sugars

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11
Q

What is mass spectrometry used for?

A

-identify proteins in cell
extracts (proteomics)
-identify posttranslational
modifications

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12
Q

Who showed that folding can be governed
by the protein itself?

A

Christian Anfinsen

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13
Q

True or False: Majority of the proteins self assemble

A

True

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14
Q

True or False: Proteins can be misfolded

A

True

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15
Q

What molecules help
misfolded proteins to re-fold properly?

A

Chaperones

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16
Q

What are chaperones also referred to as?

A

Heat-shock proteins (HSP)

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17
Q

Characteristics of heat shock proteins (HSPs) include:

A
  • Levels increase with temperature
    increase
  • More heat-resistant compared to
    average protein
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18
Q

In E. coli chaperones, how many families are involved in protein refolding?

A

3

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19
Q

What is Trigger factor (TF)?

A

A family of protein chaperones that are ribosome associated, promote folding, and prevent aggregation

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20
Q

What is GroEL and GroES?

A

A family of protein chaperones that have the following characteristics:
▪ Form stacked ring with a hollow center
▪ The protein fits inside the pore
▪ Cycles of ATP-hydrolysis cause
conformational changes to the barrel that
reconfigure the target protein

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21
Q

What is DnaK and DnaJ?

A

A family of protein chaperones that clamp down on a polypeptide to assist folding

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22
Q

True or False: Misfolded proteins are targeted for degradation

A

True

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23
Q

What processes misfolded proteins?

A

barrel-shaped Clp proteases (sense exposed by hydrophobic regions)

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24
Q

True or False: Folded proteins have different half-life

A

True

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25
What amino acids have a short half life?
Leu, Phe, Trp, Tyr
26
What amino acids have a long half life?
Asp, Glu, Cys
27
What is protein stability is correlated with?
the presence of a degron, or N-terminal aa remaining after fMet cleavage
28
True or False: Clp proteases are conserved by most organisms.
True
29
How are Clp proteases classified?
on the active site residues
30
What are the three Clp proteases?
1.Serine proteases 2.Cysteine proteases 3.Threonine proteases
31
How are Clp proteases assembled?
ATPase cap proteins (e.g. ClpA or ClpX)
32
What are Proteasomes?
protease complexes that degrade proteins
33
What is the first step of the Folding vs Degradation Triage Pathway?
DnaK and DnaJ chaperones bind to nascent protein
34
What is the second step of the Folding vs Degradation Triage Pathway?
Proteins may be folded into an active form
35
What is the third step of the Folding vs Degradation Triage Pathway?
If not folded properly, the protein can be fed to GroEL for remodeling
36
What is the fourth step of the Folding vs Degradation Triage Pathway?
If still not properly folded, the protein may be passed through proteases through degradation
37
True or False: Bacteria secrete proteins to influence their environment
True
38
Secreted proteins are proteins that are translocated across the inner membrane and end up in:
* periplasm * cross-linked to the cell wall * anchored in the outer membrane * released into the milieu/environment
39
Secreted proteins usually contain:
a signal peptide at the N-terminus that targets these proteins to be translocated across the inner membrane
40
What can target proteins destined for the cell-wall or outer membrane?
amino acid sequence motifs
41
What is present for Sec-dependent translocation across membrane?
signal peptides
42
What charge is the n-region?
positive
43
Is the h-region hydrophilic or hydrophobic?
hydrophobic
44
What processes the c-region?
signal peptidase (SPase)
45
What are some other amino acid motifs?
*Sorting signal for cell-wall anchoring * LipoBox for anchoring in the membrane
46
What are the two major secretion pathways in bacteria?
* General Secretion (Sec) pathway *Twin Arginine Translocase (TAT) pathway
47
What does the General Secretion (Sec) pathway secrete?
unfolded proteins
48
What does the Twin Arginine Translocase (TAT) pathway secrete into the periplasm?
folded proteins
49
True or False: Both, membrane proteins and secreted proteins employ Sec pathway
True
50
What do proteins destined to be incorporated into the inner membrane employ?
cotranslational Sec pathway
51
Hydrophobic transmembrane domains can incorporate into the membrane bilayer through what channel?
SecYEG lateral channel
52
What do proteins destined to be secreted into the periplasm employ?
general SecA-dependent pathway
53
What components are involved in the general SecA-dependent pathway?
*SecB pilot protein (chaperone) * SecA (has ATPase activity) * SecYEG translocon
54
Where is the peptide is completely translated?
Cytoplasm (post-translational export)
55
The completed pre-protein is then captured by what?
piloting protein called SecB
56
SecB unfolds and delivers the protein to _______ (w/ ATP) , which is associated with the _______________.
SecA, SecYEG translocon
57
What cleaves off the signal peptide to release a mature protein?
Signal peptidase
58
True or False: A proton motive force (PMF) is used to move the signal sequence of the folded protein through the TatA translocase and into the periplasm
True
59
What happens to some proteins in gram negative bacteria that end up farther than the periplasm?
* Incorporate into the outer membrane (E.g. outer membrane proteins (OMPs) * Exported out of the cell completely (E.g. nutrient acquisition proteins, toxins)
60
True or False: Different bacteria have evolved different secretion mechanisms beyond the periplasm.
True
61
What type of proteins usually form beta-barrel structures?
outer membrane proteins (OMPs)
62
What stops OMP aggregation in the periplasm?
Chaperones
63
What function does the Beta Barrel Machine (BAM) serve?
facilitates assembly of OMPs in the outer membrane
64
What are Type I secretion systems in gram negative bacteria?
ABC type transporters and are the simplest of known secretion systems
65
What are characteristics of ATP-Binding Cassette (ABC) transporters?
* Outer membrane channel * Periplasmic protein * ATP-binding protein at the inner membrane
66
What type of gram positive bacteria utilize the type 7 secretion system?
Actinobacteria and Firmicutes
67
T7SS translocon:
* Inner membrane * at least 4 subunits * Conserved ATPase EssC
68
A subset of specialized proteins that lack Sec-dependent signal peptides that is secreted in the type 7 system?
WXG and LXG
69
What roles does the type 7 secretion system serve in bacteria?
pathogenesis and competition between bacteria

Microbiology (11 decks)

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