Protein function and synthesis

Question 1

Glycosylation

Answer 1

covalent addition of sugar moietites to proteins which is required for their function and/or cellular localization

Question 2

Glycation

Answer 2

Covalent addition of aldose or ketose to proteins resulting in advanced glycated end (AGE)-modified proteins via Maillard/Amadori reactions
-associated with alterations of protein properties during aging and diabetes

Question 3

Sulfation

Answer 3

Transfer of a sulfate group on TYR from the universal donor PAPS catalyzed by Tyrosylprotein Sulfotransferase
-Role: secretion of various endocrine peptides gastrin, CCK, calcitonin

Question 4

Phosphorylation

Answer 4

Addition of a phosphate group
-serine/threonine phosphorylation
-Tyrosine Phosphorylation

Role: rapid regulation of protein activity, protein movement and localization, protein-proteins interaction: enzyme, transcription factors, translocation factors, receptors, transporters, carriers, signaling factors

Question 5

Prenylation

Answer 5

Transfer of farnesyl or geranyl group on a cystein residue present in the CAAX consensus sequences
Role; targeting and anchoring proteins to membrane

Question 6

Fatty Acylation

Answer 6

Transfer of palmitate on Cys residues with the formation of a thioester bound (reversible/irreversible) and transfer of myristate on G residues with the formation of an amide bond (irreversible)
ROle: targeting and anchoring proteins to membrane

Question 7

Describe the ubiquitination process

Answer 7

1. Attachment of activated ubiquitin by E1, a subunit of ubiquitin enzyme system, which hydrolyzes ATP to form a thiol ester with the carboxy end of ubiquitin. This activated ubiquitin is transferred to another protein, E2, referred to as ubiquitin-conjugating enzymes
2. The carboxy end of ubiquitin is ligated by E3 to a protein substrate that is ultimately to be degraded. E3 has two distinct sites that interact with a targeted protein’s N terminal amino acid

Question 8

List the four ways proteins synthesis is regulated

Answer 8

1. Hormonal effects
2. Slow vs Fast proteins
3. Plant vs animal proteins
4. mTOR regulatory mechanisms

Question 9

How does insulin and growth hormone affect protein

Answer 9

1. Insulin: increases with feeding, stimulates synthesis of protein and inhibits protein degredation, regulates imitation and translation of mRNA by regulating phosphorylation of imitation factors
2. Growth hormone: long term regulation of growth, causes production of insulin like growth factors of -1 and 2 by liver and other tissues to regulate specific proteins

Question 10

How does testosterone affect protein

Answer 10

promotes protein synthesis in muscle by regulation transcription

Question 11

How do stress hormones affect protein

Answer 11

catabolic in nature

Question 12

Cortisol and glucagon can ____ protein synthesis

Answer 12

inhibit

Question 13

Higher glucagon levels in liver facilitate synthesis of ____ ____ involved in ____ and ______

Answer 13

higher glucagon levels in liver can facilitate synthesis of hepatic enzymes involved in gluconeogenesis and ureagenesis

Question 14

Increase in cortisol promote muscle protein catabolism to

Answer 14

shuttle AAs for gluconeogenesis

Question 15

Slow vs fast proteins affect

Answer 15

-digestion and absorption
-rate of appearance of AA in plasma
-subsequent utilization of AA within cells

Question 16

Fast protein

Answer 16

Whey, soy, AA mixtures, protein hydrolysates
-better stimulates MPS and whole body protein synthesis at rest and following resistance training

Question 17

Slow protein

Answer 17

casein- lower and more prolonged plasma AA concentrations - reduce protein breakdown

Question 18

Plant vs animal protein

Answer 18

-Animal proteins higher in Leucine (greater stimulation of MPS
-postprandial concentrations of AA that do not contain all essential AA thought to reduce AA availability to tissues, stimulate hepatic oxidation of AA, stimulate ureagenesis

Question 19

mTOR

Answer 19

mammalian target of rapamycin
-large proteins kinase complex that functions in many cellular protein processes involving cell growth/proliferation

-amino acids (leucine and arginine) participate in regulation of mTOR activity which in turn regulate protein synthesis

Question 20

List out protein functions

Answer 20

1. catalysts (enzymes)
2. Messengers
3. structural elements
4. buffers
5. Fluid balancers
6. immunoprotectors
7. Transporters
8. Acute phase responders
9. Cell adhesion, conjugated proteins