Post-translational modifications Flashcards

1
Q

What is meant by post-translational modifications?

A

Processing that proteins undergo after translation

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2
Q

What are the types of post-translational modifications?

A

Proteolytic cleavage

Chemical modification

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3
Q

What is meant by proteolytic cleavage?

A

Breaking peptide bonds to remove part of the protein

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4
Q

What is meant by chemical modification?

A

Additional of function groups to protein

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5
Q

What are some examples post-translational modifications that occur in the ER?

A

Proteolytic cleavage

Forming disulphide bonds

N-linked glycosylation

Hydroxylation

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6
Q

Disulphide bonds are formed between what amino acid?

A

Cysteine

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7
Q

What is the enzyme responsible for forming disulphide bonds?

A

Protein disulphide isomerase

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8
Q

What is glycosylation?

A

Addition of sugar molecules to amino group -NH2

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9
Q

What is hydroxylation?

A

Addition of hydroxyl group -OH to protein

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10
Q

What is an example of a modification that occur in the Golgi apparatus?

A

O-linked glycosylation

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11
Q

What is O-linked glycosylation?

A

Attachment of sugar to hydroxyl group -OH

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12
Q

What is the importance of glycosylation?

A

Correct protein folding

Interaction with other molecules

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13
Q

What do problems with glycosylation lead to?

A

Congenital disorders of glycosylation, CDGs

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14
Q

What is produced when the mRNA of the insulin gene is translated?

A

Preproinsulin

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15
Q

Which ribosomes produce insulin?

A

Ribosomes on the ER

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16
Q

What happens to preproinsulin in the ER?

A

Signal peptide is cleaved off to form proinsulin

2 disulphide bonds formed bewtwen A chain and B chain
1 disulphide bond formed at A chain

17
Q

Where is proinsulin transported to form the ER?

18
Q

What happens to proinsulin in the Golgi?

A

C chain is cleaved off to produce insulin

19
Q

How does proteolytic cleavage create different proteins?

A

Cleavage at different sites

can produce different proteins of different lengths

20
Q

What can cause misfolding of a protein?

A

Mutations in gene producing protein with different amino acid sequence primary structure

Protein trapped in misfolded conformation

21
Q

What is responsible for correcting misfolded proteins?

A

ER chaperone proteins

22
Q

What happens to a misfolded protein if it cannot be corrected by ER chaperone proteins?

A

Protein returned to cytosol for degradation

Protein accumulates in ER, causing disease

23
Q

What are the types of secretion?

A

Constitutive

Regulatory

24
Q

What is constitutive secretion?

A

Proteins being continuously secreted

25
What is regulated secretion?
Proteins secreted when they are needed
26
What are the three examples of proteins secreted constitutively?
Collagen Albumin Immunoglobulin
27
What are three examples of proteins secreted regularly?
Insulin Glucagon ACTH