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MGD > session 7-protein processing and targeting > Flashcards

session 7-protein processing and targeting Flashcards

1
Q

what is regulated secretion?

A

protein released in response to a signal e.g. hormone

packaged into vesicles but not released until stimulus received e.g. insulin

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2
Q

in which situation are ribosomes attached to ER?

A

when proteins are destined for secretion out of the cell or digested. e.g. CSM, lysosome and secretory vesicle

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3
Q

in which situation do ribosomes remain cytosolic?

A
  • if proteins are to remain in cytosol

- import into other organelles e.g. mitochondria, chloroplasts and nucleus

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4
Q

what is swyer syndrome?

A
  • loss or mutation of NLS (nuclear localisation signal) in sex determining region
  • genotype=XY but outwardly female
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5
Q

what symptoms are observed with Leri Weill dyschondrosteosis and Langer mesomelic dysplasia (LAMDer)? (Nuclear)

A

-short stature
-due to mutation on NLS of SHOX transcription factor
SHOX is required for skeletal development

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6
Q

What symptoms are shown amongst people with RCP (rhizomelic chondrodysplasia punctata)? (Peroxisomal)

A
  • skeletal abnormalities
  • facial abnormalities
  • intellectual disability
  • resp problems
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7
Q

what enzyme cleaves a signal?

A

signal peptidase

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8
Q

what type of Glycosylation occurs during modifications in ER?

A
  • disulphide bond formation

- N linked Glycosylation (sugars added to asparagine side chain-onto nitrogen)

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9
Q

why is glycosylation of proteins important?

A
  • correct folding
  • stability
  • deficiencies in n linked glycosylation can lead to severe inherited disease
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10
Q

what type of glycosylation occurs in the golgi and what modifications?

A
  • o linked
  • proteolytic cleavage
  • trimming of n linked oligosaccharides
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11
Q

what is the name of the molecule that the oligosaccharide needed for n linked Glycosylation is built up on?

A

dolichol phsphate carrier

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12
Q

what happens in o linked glycsylation?

A

attachment of sugar to -OH group of serine and threonine

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13
Q

where does pre segmentation occur and what terminal is removed?

A

-in ER and N terminal is removed

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14
Q

where does pro segmentation occur?

A

-golgi

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15
Q

to form covalent crosslinks amongst collagen, what enzyme is used?

A

lysyl oxidase

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16
Q

what does lysyl oxidase require?

A

vitamin B6 and Cu2+

17
Q

what is ehlers danlos syndrome (EDS) and why does it occur?

A
  • mutation in type 5 collagen

- lysyl oxidase deficiency

18
Q

what 2 enzymes are used in lysosomal targeting?

A

N-acetylglucosamine phototransferase (AGPT)

N-acetylglucosamine photoglycosidase (AGPG)

19
Q

why does I cell disease occur?

A
  • defects with N-AGPT enzyme resulting in lack of M6P receptor addition to lysosome destined protein
  • results in lysosomal proteins accidentally miss targeted for secretion=large amounts in blood and urine
20
Q

sometimes proteins that are meant to be resident within the lumen of the ER (e.h. signal peptidase), are lost when vesicles are pinched off and transported to the golgi. How can these be retrieved?

A
  1. specific protein sequences (KDEL) bind to KDEL receptors in golgi (enhanced by LOW PH in golgi)
  2. returned to ER as transport vesicles
  3. dissociate in ER at neutral PH conditions
  4. KDEL receptor transported back
21
Q

what is constitutive (continuous) secretion?

A

proteins packaged into vesicles that are released continuously by exocytosis

22
Q

What is protein processing and targeting?

A

See notes on penultimate

23
Q

Out of the 4 target organelles, state which keep and which do not keep their localising signals blinded. ER, mitochondria, peroxisome, nucleus.

A

Cleaved, cleaved, retained, retained

24
Q

What protein assists in disulphide bond formation?

A

PDI-protein disulphide isomerase

25
Q

Is PDI a KDEL protein and if yes, what does this mean?

A

Yes, can be retained in lumen of ER

26
Q

What enzyme increases h bonding between each alpha polypeptide to form collagen?

A

Prolyl hydroxylase

27
Q

What does prolyl hydroxylase require and how does scurvy relate to this?

A

Vitamin c and Fe2+

Scurvy-vit c deficiency and so tropocollagen triple helices are weak

MGD (11 decks)

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