Question

Your laboratory has just gained the license to allow you to research, and commercialize the results for, a novel Protein 18(p18). Because there is very little known about this protein, you need to characterize the protein.

You are provided with:

the human cDNA corresponding to the protein,

a Chinese Hamster Ovary (CHO) cell line expressing the cDNA for the p18,

and the amino acid sequence (using the one-letter code) of the p18.

Shown following is the first 30 amino acid region of this putative amino acid sequence for p18:

¹YFNPS     ^6TSDWPT    ¹¹LAPAN    ¹⁶YTFLF    ²¹FLARY    ²⁶WYINL³⁰

1. Based on the partial amino acid sequence provided for p18,

a. which amino acids in the sequence provide may be glycosylated and how can you identify these potential sites? 


b. and with which type of glycosylation might they be modified? 


c. and explain how these modifications are made, 


d. and explain where these modifications are made in the cell,


e. and finally, explain what effects glycosylation might have on the protein.

Answer 1

1.
Glycosylation sites:
Tyrosine(Y)
Aspargine (N)
Serine (S)
Threonine (T)

2.
O-linked glycosylation sites:
Tyrosine(Y)
Serine (S)
Threonine (T)

N-linked glycosylation sites:
Aspargine (N)

3.
It is a post-translational modification. Once the protein is synthesized completely, it is subjected to glycosylation by an enzyme known as the glycosyltransferase.
Protein + UDP-Glc ------> Protein-Glc

4.
ER and Golgi are the sites of post-translational modifications in the cell.

5.
Glycosylation can affect,
a. Protein localization
b. Stability
c. Interactions with other proteins
d. Activation or inhibition of function