Kandpal - Protein Targeting and Vesicular Trafficking Flashcards

1
Q

what do the ribosomes do that are free in the cytosol

A

synthesize cytoplasmic, nuclear, and mitochondrial proteins

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2
Q

what do the bound/ER ribosomes synthesize

A

secreted proteins, plasma membrane proteins, ER proteins, golgi proteins and lysosomal proteins

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3
Q

what is a nuclear localization sequence (NLS) on a protein

A

either a signal sequence on the N-terminal or a signal patch in the center of the protein that are hydrophobic

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4
Q

what is the signal hypothesis

A

translation in the presence of ribosomes = larger proteins and in the presence of microsomes = smaller proteins

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5
Q

what are 3 types of protein traffic

A

gated transport, transmembrane transport, and vesicular transport

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6
Q

where does gated-transport occur, how does protein enter and does it require ATP

A

cytosol -> nucleus, through pore complexes (nucleoporins), yes

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7
Q

how do import receptors work in gated transport

A

protein NLS binds to nucleoporin -> cargo is delivered to nucleus -> Ran-GTP binds to receptors -> leaves nucleus -> Ran-GDP dissociates from receptor

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8
Q

how do export receptors work in gated transport

A

Ran-GTP binds to receptors -> protein + nuclear export signal leave nucleus -> Ran-GDP dissociates and cargo is delivered to cytosol

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9
Q

what regulates GTP and GDP in gated transport

A

GTPase activating protein (GAP) in cytosol and guanine exchange factor (GEF) in nucleus

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10
Q

in the transmembrane transport from cytosol to mitochondria, what is the signal peptide and where is it located

A

a helical structure with + charged clusters on one side and - charged regions on the other
at the N-terminus

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11
Q

what 2 things are located on the outer membrane for transmembrane transport

A

TOM (translocation channel/receptor) and SAM complex

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12
Q

what 2 things are located on the inner membrane for transmembrane transport

A

TIM 23 complex (Hsp70 import ATPase) and OXA complex

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13
Q

where is the signal located for cytosol-> peroxisome transport

A

3 amino acid sequence at the C-terminus

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14
Q

what happens in peroxisome transport disorder -> Zellweger Syndrome

A

mutations in transport protein Pex2 - leave empty peroxisomes

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15
Q

which type of transmembrane transport has translation and translocation at the same time

A

cytosol -> endoplasmic reticulum

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16
Q

what recognizes the signal sequence in the cytosol for ER transport

A

signal recognition particle (SRP) - complex 300 nucleotides, 7SL RNA and 6 proteins

17
Q

after SRP recognizes signal sequence in cytosol for ER transport - what does the protein bind to

A

binds on the nascent protein, large ribosomal unit and SRP receptor (Methionine residues on p54 bind to signal sequence) and hydrolyzes GTP

18
Q

there are 4 topological classes or proteins (cytosol -> ER space/lumen) what are the based on

A

classified by orientation, transmembrane domains, and signal sequences

19
Q

what is the cleavable signal on Type 1 topological protein

A

cleavable signal is “COO-“ on cytosol and the hydrophobic residues stop transport and gets embedded into membane

20
Q

what is the cleavable signal on Type 2 topological protein

A

no cleavable signal - but NH3+ is in cytosol

21
Q

what is the cleavable signal on Type 3 topological protein

A

no cleavable signal but has hydrophobic regions that stop transport and get embedded into membrane

22
Q

what is the cleavable signal on Type 4 topological protein

23
Q

secretory proteins have a coat in vesicular transport, what are the 3 types of coats

A

clathrin, COPI, and COPII

24
Q

what are the steps for vesicle formation and fusion in vesicular transport

A

coat-recruitment by GTPase control, Rab proteins regulate flow of vesicle to correct membrane and SNARE proteins mediate fusion

25
what are the 2 paths for secretory proteins
constitutive pathway or regulated pathway
26
what happen in the constitutive pathway (unregulated) for secretory proteins
after golgi sorts into vesicles -> has unregulated fusion into extracellular space (occurs all the time)
27
what regulates the regulated pathway in secretory proteins
hormone or neurotransmitter (only occurs when signal occurs)
28
what do lysosomes store
hydrolytic enzymes - glycosidases, proteases, phosphatases, and sulfatases
29
what "tag" do lysosomal hydrolases carry
unique "mannose-6P" tag on N-linked oligosaccharide that is recognized by receptor on lysosome
30
what is I-cell disease
lysosomal storage disease
31
what happens with a deficiency of mannose-6P attaching enzyme
no transport of lysosomal enzymes to lysosomes -> accumulation in circulation
32
what are 3 endocytic pathways
phagocytosis, pinocytosis, and receptor-mediated endocytosis
33
what is autosomal dominant hypercholesterolema caused by
mutations in LDL (low density lipoprotein) receptor - which normally removes LDL from circulation
34
what are 2 protein modifications that occurs after translation
glycosylation at OH groups of serine and theronine residues (O-linked) or amide group of asparagine (N-linked) and disulfide bonds are added for folding
35
what does a1-antitrypsin do (secreted from hepatocytes and macrophages)
inhibits trypsin and blood pretease elastase
36
what does a deficiency in a1-antitrypsin cause
hereditary emphysema - and an absence leads to elastase degrading lung tissue