4 You perform a series of experiments on the synthesis of th

4. You perform a series of experiments on the synthesis of the primary hormone prolactin, which is a single polypeptide chain 199 amino acids long. The mRNA coding for prolactin is translated in a cell- free protein synthesizing system containing ribosomes, amino acids, tRNAs, aminoacyl-tRNA synthetases, ATP, GTP and the appropriate initiation, elongation and termination factors. Under these conditions, a polypeptide chain 227 amino acids long is produced. . a) How might you explain the discrepancy between the normal length of prolactin and the length of the polypeptide you synthesized? b) What components are missing from this protein synthesizing system that would partially account for the discrepancy?

Solution

Since the translation is performed in a cell free protein synthesizing system, it is obvious that the regulation of protein synthesis have been avoided.

In this experiment, all the exon and intron have been translated so that inspite of producing 199 amino acid chain, a chain of 227 amino acid have been produced.

Protein synthesis regulatory components are missing in this protein synthesizing system and this would lead to the discrepancy in the length of the polypeptide chain.