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MCBG > Session 9: Post-translational Modification and Protein Targeting > Flashcards

Session 9: Post-translational Modification and Protein Targeting Flashcards

1
Q

What is post-translational modification?

A

The processing that some proteins undergo following their production via translation

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2
Q

Where are some common subcellular locations of protein targeting for sorting?

A

Endoplasmic reticulum
Lysosomes
Mitochondria
Nucleus

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3
Q

What 4 things are required for protein sorting?

A

A signal
A receptor that recognises the signal and directs to the correct membrane
Translocation machinery
Energy to transfer the protein to its new place

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4
Q

What is the nature of signal targeting proteins to the ER?

A

A signal sequence that is recognised by SRP during translation

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5
Q

What is the location of the signal within the primary sequence of proteins destined for the ER?

A

N- terminus

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6
Q

Is the protein folded or unfolded during transfer to the ER?

A

Unfolded

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7
Q

What specialist proteins are involved in targeting proteins to the ER?

A

Signal Recognition Protein (SRP)

SRP receptor

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8
Q

Is the signal retained or cleaved once it reaches the ER?

A

Cleaved by signal peptidase

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9
Q

Does the process of targeting proteins to the ER require energy?

A

Yes. the hydrolysis of GTP by SRP

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10
Q

What is the nature of the targeting signal needed to direct proteins to the nucleus?

A 
Nuclear Localising Signal (NLS)
Basic sequence (Arg/Lys)
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11
Q

Where is the primary sequence of the targeting signal located on proteins destined for the nucleus?

A

On the surface of folded protein

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12
Q

Are the proteins that are destined for the nucleus folded or unfolded during transfer?

A

Folded

They pass through large pores in the nuclear membrane

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13
Q

What specialist proteins are involved in the trafficking of proteins to the nucleus?

A

Carrier protein: Importin

RanGTP

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14
Q

Is the signal retained or cleaved once it reaches the nucleus?

A

Retained

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15
Q

Does the process of targeting signals to the nucleus require energy?

A

Yes, the hydrolysis of GTP

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16
Q

What is the nature of the targeting signal that sends proteins to mitochondria?

A

It is an amphipathic signal that targets proteins to the matrix

17
Q

What is the location of the signal within the primary sequence of proteins destined for mitochondria?

A

N-terminus

18
Q

Are the proteins that are destined for mitochondria folded or unfolded during transfer?

A

They are held partially folded by chaperones

19
Q

What specialist proteins are involved in the trafficking of proteins to the mitochondria?

A

MSF

Tom and Tim

20
Q

Is the signal retained or cleaved once the protein has been delivered to mitochondria?

A

The signal is cleaved

21
Q

Does the process of targeting signals to mitochondria require energy?

A

Yes, requires ATP

22
Q

What is the nature of the targeting signal needed to direct proteins to lysosomes?

A

Post translational addition of Mannose-6-Phosphate

Phosphate is added to 6th carbon on mannose sugar in the golgi

23
Q

Where is the primary sequence of the targeting signal located on proteins destined for lysosomes?

A

Must be signal patch to distinguish lysosomal proteins from other mannose-labelled proteins

24
Q

Are the proteins that are destined for the nucleus folded or unfolded during transfer to lysosomes?

A

Folded (delivered via vesicle)

25
Q

What specialist proteins are involved in the trafficking of proteins to the lysosomes?

A

M6P receptor in the trans-golgi

26
Q

Is the signal retained or cleaved once the protein has been delivered to lysosomes?

A

Phosphate is removed by phosphatase

27
Q

Does the process of targeting signals to lysosomes require energy?

A

The process requires INDIRECT use of ATP to remove the phosphate

28
Q

What is the nature of the targeting signal needed to retain proteins in the ER?

A

KDEL

29
Q

Where is the primary sequence of the targeting signal located on proteins destined to be retained in the ER?

A

C-terminus

30
Q

Are the proteins that are destined for the nucleus folded or unfolded during ER retention?

A

Folded (delivered via vesicle)

31
Q

What specialist proteins are involved in the trafficking of proteins to be retained in the ER?

A

KDEL and KDEL receptor in cis-golgi

32
Q

Is the signal retained or cleaved once the protein is retained in the ER?

A

Retained

33
Q

Does the process of retaining proteins in the ER require energy?

A

No, no energy is required

MCBG (9 decks)

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