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MIP 443 > Lecture 14 -- Protein Transport and Secretion > Flashcards

Lecture 14 -- Protein Transport and Secretion Flashcards

1
Q
  • SEC dependent pathway

- Twin-arginine pathway (TAT)

A

List the pathways only involved in translocation

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2
Q
  • Types I, II, IV, VI

- Type VII

A

List the pathways responsible for translocation and secretion in one step

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3
Q
  • Type II (uses TAT or SEC)

- Type V (SEC)

A

List the translocation linked secretion pathways (two steps)

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4
Q
  • allow for formation of cell surface structure (cell wall, cell membrane, capsule)
  • nutrient acquisition
  • pathogenic mechanisms (infection of host cells)
  • competition with other bacteria
A

Why do bacteria export/secrete protiens?

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5
Q
  • Type I pilus
  • Toxins/adhesins
  • P-type pilus
  • Curli
  • OMPs/adhesins
A

Structures involved in virulence

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6
Q
  • siderophore receptors

- TonB-dependent iron-uptake receptors

A

Nutrient receptors

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7
Q
  • many exported/secreted proteins are hydrophilic

- for proper localization and regulation of release

A

Why do bacteria need mechanism of protein secretion

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8
Q

Proteins that are translocated across the cytoplasmic membrane

A

Exported proteins

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9
Q

Proteins translocated across the cytoplasmic membrane and subsequently transported across the entire cell envelope

A

Secreted proteins

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10
Q

cytoplasmic membrane, cell wall, *capsule, environment

A

List the potential locations where proteins can end up in gram positive bacteria

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11
Q

cytoplasmic membrane, periplasm, cell wall, *outer membrane, capsule, environment

A

List potential locations where proteins can be brought in gram negative and cutoff for secretion

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12
Q
  • protein folded in the cytoplasm (stays intracellularly)
  • intrinsically disordered proteins (rare)
  • unfolded proteins are exported/secreted
  • folded proteins are exported/secreted
A

List the four pathways proteins can take after translation

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13
Q
  • targeting and sorting in the cytoplasm
  • translocation through a channel/energy in the membrane
  • maturation and release in the periplasm (and potential folding)
A

List the steps of translocation/what happens a each location

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14
Q
  • universal, most well studied mode of translocation
  • proteins are in an unfolded state
  • essential for viability (cannot be deleted from cell)
  • all proteins have a signal sequence
A

SEC-dependent protein translocation

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15
Q
  • Co-translational

- Post-translational (chaperone dependent and independent)

A

What are the two modes of SEC mediated translocation

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16
Q
  • integral membrane protein in SEC pathway
  • generates a gated pore (the channel)
  • made up of many alpha helices
  • essential
A

SecYEG

17
Q
  • involved in the sorting and recognition of the signal peptide in the SEC pathway (binds preprotein)
  • provides the energy for translocation (ATPase) (along with Ftsy)
  • can act as a chaperone to stabilize the unfolded protein in the cytoplasm
  • essential
A

SecA

18
Q
  • protein being secreted in SEC pathway
  • has signal sequence
  • unfolded
A

Preprotein

19
Q
  • GTPase provides the energy
  • ribosome localizes to the membrane
  • sorting and targeting (1) –> translocation (2) –> maturation (3)
  • signal peptidase cleaves protein so folding can occur
A

Co-translational Sec Pathway

20
Q
  • maintain proteins in an unfolded state
  • bind the signal peptide in the cytosol or ribosome
  • bind SecA
A

Function of chaperones

21
Q
  • plug in place when these two proteins are not interacting

- plug opens when they interact

A

SecYEG-SecA complex

22
Q
  • non-essential for SEC translocation but improves efficiency
  • may help release the signal sequence from the SecYEG channel
  • may help formation of SecYEG
A

SecDF-YajC

23
Q

negatively charged glutamic acid group interacts with positive charge, pulling the protein through (uses ATP)

A

PMF electrophoresis

24
Q

Lysine is negatively charged at the base and becomes positively charged with the addition of a hydrogen (cannot go back through the channel) – uses ATP

A

PMF proton ratchet

25
Q
  • less common translocation system
  • translocates folded proteins
  • requires a signal sequence
  • not essential but can affect proper cell function
  • ATP independent (only driven by PMF)
A

Twin Arginine Translocation (TAT) System

26
Q
  • forms pore structure through which proteins move
  • interacts with the signal peptide and folded protein
  • serves as the initial docking site of the signal peptide
A

Functions of TAT A, TAT B, and TAT C

27
Q

Only certain cofactors are found inside the cell

A

Why do proteins fold inside the cell?

28
Q
  • Signal Peptidase I cleaves signal peptide

- Signal Peptidase II cleaves signal peptide from pre-lipoproteins

A

What happens after translocation?

29
Q
  • charged n region with Arg/Lys, binds to heads of phospholipids
  • hydrophobic h region that associates with acyl chains of phospholipids
  • c region (BXZ) where b and z are small amino acids
A

Standard signal peptide components

30
Q
  • n region
  • h region
  • c region (cleavage domain) “BXZ” where B is large hydrophobic and cysteine is +1
A

Lipoprotein signal peptide components

31
Q
  • 1st is diacylation

- 2nd is acylation

A

steps for the addition of groups to cysteine

32
Q
  • twin arginine RR

- longer and less hydrophobic than Sec signal sequence

A

TAT signal peptide components

33
Q
  • donates for the diacylation from phosphatidylglycerol
A

Lgt

34
Q
  • removes signal peptide for lipoproteins
A

Lsp

35
Q
  • donates for the final acylation in lipoproteins
A

Lnt

MIP 443 (14 decks)

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