Suppose, you synthesized RNA in vitro using polynucleotide phosphorylase, 3 part
ID: 261783 • Letter: S
Question
Suppose, you synthesized RNA in vitro using polynucleotide phosphorylase, 3 parts ADP and one part GDP. After the reaction, you isolated all RNA molecules and translated them in a cell-free translation system. Now, answer the following questions. (A) How many different amino acids do you expect in the polypeptides synthesized in the cell-free system?Name these amino acids. Use the codon dictionary available in the textbook. (B) Which amino acid would show highest frequency of incorporation in the polypeptides synthesized in the cell-free system? Show your calculations for full credit.
Explanation / Answer
Kindly find explanation to both answers below as a note of this experiment:
Polynucleotide phosphorylase (PNPase) is multifunctional enzyme and possess exoribonuclease activity. However, it is believed that it degrades RNA with the excess of inorganic phosphates present in the cells. In case of availability of nucleoside diphosphate, it synthesizes RNA. In most cases, however, it is considered to be the m RNA degradation component. Since only available nucleoside diphosphates in the given case are ADP and GDP, considering no others available, since it is a cell-free system, the amino acids that will be formed will be from various combinations between the codons formed by A and G.
AAA - Lysine
AAG – Lysine
AGA – Arginine
GAA – Glutamic acid
GGA – Glycine
GGG – Glycine
3 parts ADP and 1 part GDP has been used in the synthesis of RNA. This will mean that ¾ of the protein that is made will contain A. Besides, PNPase is known to bring about polyadenylation. Given this, the chance is such that Lysine will be the most synthesized or coded amino acid, since 2 out of 6 amino acids listed above code for Lysine. Glycine will not be produced as much because the ratio of G that is added in the growing protein chain is only 1/4TH the total sequence.
In absence of molecular weight or bond cleavage details, estimation of the exact length or amino acid residues will be difficult.
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