week 2 - post translational modifications

Question 1

what is glycosylation

Answer 1

the addition of sugars to the side chains of certain amino acids

Question 2

what is N-linked glycosylation important for

Answer 2

1. protein folding
2. protein targeting
3. occurs initially in the ER and is refined by the golgi

Question 3

what is O-linked glycosylation important for

Answer 3

1. complementary to phosphorylation and enhance protein-protein interactions
2. mostly occurs in the cytoplasm

Question 4

what is ubiquitylation

Answer 4

modification that enables diverse quantitative and reversible regulation

Question 5

what is phosphorylation

Answer 5

plays critical roles in the regulation of many cellular processes such as cell cycle, growth, apoptosis, signal transduction pathways

a phosphate group (PO4) is reversibly attached to an amino group using a protein kinase

Question 6

what is dephosphorylation

Answer 6

reverse phosphorylation reaction, removal of phosphate group

protein returns to original conformation and activity
catalysed by protein phosphatases (enzyme)

Question 7

what are protein kinases

Answer 7

an enzyme that takes phosphate groups from ATP and adds it to a protein

Question 8

what is proteolysis important for
(PTM)

Answer 8

1. making different variations (isoforms) of a protein from single mRNA
2. converting proteins to there active form
3. enhancing proper folding of a protein
4. enhancing insertion of protein to membranes or lumen of organelles

Question 9

what is covalent addition of molecules important for
(PTM)

Answer 9

1. enhancing/disrupting interaction with other proteins
2. enhancing stability or degradation
3. enhancing transportation

Question 10

what is insulin maturation
(proteolysis example)

Answer 10

when insulin is translated from mRNA to its active form

Question 11

insulin maturation steps

Answer 11

1. body produces insulin to remove glucose from food
2. insulin is promoted by proteins in the pancreas
3. prepoinsulin must be converted before entering the bloodstream
4. insulin travels through vesicles to function round the body

Question 12

what are histones important for

Answer 12

1. DNA packaging
2. PTM of histones are essential for gene expression
3. acetylation and methylation of histones causes relaxation or condensation of nucleosomes
4. DNA is negatively charged, histones are positively charged - drives the attraction

Question 13

activation of CDK protein through phosphorylation steps

Answer 13

phosphorylation of CDK - cyclin complex activated target proteins;

1. cyclin binds and activates CDK
2. CDK activates target proteins to regulate cell cycle
3. cyclin destroyed

Question 14

what are phosphatases

Answer 14

enzymes that remove phosphate groups