Lecture 12

Question 1

Preproinsulin is converted to proinsulin in the ER where the _____ sequence is removed. Then, proinsulin becomes insulin in the golgi where the ____ chain is cut out, leaving behind the ____ and ____ chains connected by _____ bonds. _____ _______ is an autosomal dominant disorder in which _____ cleavage is defective, leading to equal amounts of insulin and partially cleaved ______ in the blood. Heterozygotes are NOT diabetic.

Answer 1

Signal sequence

C chain

A

B

Disulfide

Familial Hyperproinsulinemia

Proinsulin

Proinsulin

Question 2

Insulin’s ___ peptide is relatively stable in plasma and can be used to distinguish between DM type 1 and 2.

Answer 2

C peptide

Question 3

In the clotting pathway, ____ and factors ___, ____, and ____ contain gamma-carboxylation residues formed by vitamin ___.

Answer 3

Prothrombin

VII

IX

X

Vitamin K

Question 4

_____ is a virus that takes advantage of inactivation of proteins via proteolytic cleavage. It’s protease cleaves ____, which reduces cap-dependent scanning and thus translation of host cell proteins. The resultant cleaved protein (___) can still initiate translation of the viral proteins via ______.

Answer 4

Polio

eIF4G

4G (Polio doesn’t need LTE; it works on that “4G”)

IRES

Question 5

Protein folding processes are accelerated by enzymes. Protein _____ isomerases (shuffle this type of bond to find the conformation most suitable for the protein..) Peptidyl ____ isomerases internconvert cis- and trans- forms of proline. _____ discourage improper interactions.

Answer 5

Protein Disufide isomerases

Peptidyl Prolyl isomerases

Chaperones

Question 6

Protein turnover is a process mediated by labeling of target proteins with ____ and subsequent cleavage by a ______. There are 3 enzymes involved with the labeling step:

1. E1 - _____ ______ enzyme
2. E2 - _____ _______ enzyme
3. E3 - _____ ______ (mainly responsibly for the specificity of the protein targeted for degradation.)

Answer 6

Ubiquitin

Proteosome

Ubiquitin Activation enzyme

Ubiquitin Conjugation enzyme

Ubiquitin Ligase

Question 7

The ____-terminal of proteins largely dictate the half-life of the protein (Serine –> >20hrs, while aspartate–> about 3mins). So to do _____ sequences (when present, the protein has a shorter half-life.)

Answer 7

N-terminal

PEST sequences