Protein Structure & Function

Question 1

how many natural amino acids?

Answer 1

20 common natural aa

Question 2

what is a peptide?

Answer 2

2+ aa linked by peptide bond.

Question 3

what is a residue?

Answer 3

name of an aa when in a ppc

Question 4

protein trafficking

Answer 4

mechanism by which cell transports proteins to appropriate locations in or outside of cell. if trafficking is incorrect, can lead to disease

Question 5

where do proteins synthesised on free ribosomes go?

Answer 5

peroxisomes, nucleus, cytosol, and mitochondria

Question 6

where do proteins synthesised on RER go?

Answer 6

to Golgi apparatus then: lysosomes, membranes, and secretion

Question 7

how are proteins transported into nucleus?

Answer 7

nuclear localisation signal enables recognition and transport through nuclear pores

Question 8

how are proteins imported into mitochondria?

Answer 8

have N-terminal mitochondrial import sequence.

Question 9

secretory protein trafficking

Answer 9

proteins for secretion have:
- N-terminal signal sequence
- 8-10 hydrophobic aa so can be embedded in hydrophobic core in membrane

Question 10

Post-transitional modifications (PTMs)

Answer 10

Changing one or more amino acids in a protein after translation.
There are over 50 types of PTM.
Alter function, cell location, and viability

Question 11

PTM - phosphorylation

Answer 11

Addition of phosphate group at serine, threonine or tyrosine.
Alters protein function and enables cell signalling
Occurs throughout cell

Question 12

PTM - glycosylation

Answer 12

Carbohydrate is attached:
- O-linked at serine or threonine (simple)
- N-linked at asparagine (complex)
Occurs in ER and Golgi apparatus
Function: Increases protein stability, helps protein folding, helps cell attachment to extracellular matrix, blocks pathogens from attacking host cells

Question 13

PTM - Ubiquitination

Answer 13

3 step enzyme cascade involving E1, E2, and E3 enzymes.
Ubiquitin transferred via its C-terminal glycine onto lysine residue NH2+ side chain.
Occurs in multiple locations in cell

Question 14

What causes protein misfolding?

Answer 14

Change in primary sequence
Escape from native folding pathway

Question 15

What is a prion?

Answer 15

A misfolded protein which causes misfolding in normal variants of the same protein which leads to its accumulation and eventually cell death.
Originates both sporadically and by transmission and inheritance

Question 16

Amyloidosis

Answer 16

When amyloid proteins are deposited in tissue and organs.
Misfolding of amyloid proteins forms fibrils w/ cross-beta structure —> can’t be degraded.

Question 17

AL Amyloidosis (1° Amyloidosis)

Answer 17

Cause: bone marrow/plasma cell disorder
Results in: overproduction of abnormal ig light chains forming amyloid
Prevalence: most common type of Amyloidosis
Treatment: treat underlying bone marrow disorder —> stops production of amyloidogenic light chains.
Monoclonal B lymphocyte proliferation —> increased plasma cells —> overproduction of IG light chains —> incomplete degradation forming AL amyloid

Question 18

AA Amyloidosis (2° Amyloidosis)

Answer 18

Cause: response to chronic inflammatory disease
Results in: Overproduction of serum amyloid A —> fragments form amyloid
Treatment: suppress inflammatory condition that triggers abnormal SAA production levels
Chronic inflammation -> macrophage activation -> IL1+IL6 production stimulating liver to produce more SAA -> incomplete degradation into AA amyloid

Question 19

Alzheimer’s - what is it?

Answer 19

Age-related neurodegenerative disease: affects memory, thinking + behaviour

Question 20

Characteristics of Alzheimer’s development

Answer 20

Extracellular amyloid-beta accumulation into plaques.
Aggregation of abnormally-phosphorylase’s tau protein into intraneuronal neurofibrillary tangles.
- Tau normally stabilises microtubules which are essential for intercellular transport and neurone structure so abnormal phosphorylation of tau leads to oligomerisation and tangle formation —> microtubules destabilisation