Question

While studying Dalalaicine 2 (Dala2) a protein expressed in very high amounts in the brain cortex of individuals who meditate regularly), you decided to develop an expression plasmid construct carrying the coding sequence for Dala2 and express the protein in two different mammalian cell lines: Wild-type HEK293A and HEK293A-K2 cells, (the latter are HEK293A cells stably transfected to over-express K2, a protein kinase that is known to recognize and modify an amino acid motif present in Dala2). To further characterize the protein, you introduced a Lysine to Alanine mutation in residue 80 of the protein (K80A), and you named the resulting mutant Dala2-K80A. The image below shows the immunoblot data obtained for Dala2 and Dala2-K80A in the two cell lines indicated above:

1 2 3 45 6 7 8 250 4S0 250 100 00-_ 50 50 37 37 -25 20 20_- 心 MS AS

Lanes 2 and 5 are wild-type Dala2, lanes 3 and 6 are Dala2-K80A, and lanes 4 and 7 are Dala2-K80A in cells treated with MG132 (a proteasomal inhibitor).

According to the data above:

1- The ~70 kDa form of Dala2 seen in lane 2 is likely to represent:

a. Phosphorylated Dala2

b. N-glycosylated Dala2

c. Dimeric Dala2

d. SUMOylated Dala2

e. O-glycosylated Dala2

2- In the presence of large amounts of the K2 protein kinase, Dala2 becomes

a. unstable and rapidly degraded

b. SUMOylated

c. Phosphorylated

d. Membrane-associated

e. Poly-ubiquitinylated

Answer 1

ANSWER

According to the reference data:

1- The ~70 kDa form of Dala2 seen in lane 2 is likely to represent:

a. Phosphorylated Dala2

2- In the presence of large amounts of the K2 protein kinase, Dala2 becomes

a. unstable and rapidly degraded