You perform a third experiment, in which you add both SRP and ER membrane vesicles to your protein-synthesizing system, and find
that translation of the prolactin mRNA now produces a polypeptide 199 amino acids long. What is the explanation of the results? Where would you expect to find this polypeptide? Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Terms can be used once, more than once, or not at all.
SRP binds to the ER signal sequence of the newly forming polypeptide chain and halts protein synthesis, thereby preventing the chain from growing beyond 199 amino acids. Upon docking, the nascent peptide chain is inserted into the translocon channel where it enters into the ER. Protein synthesis resumes as SRP is released from the ribosome without this a complete pre prolactin chain might be produced.
