You are utilizing a cell culture system derived from a breast cancer tumor to examine the process of protein synthesis. You discover that short peptides are present in the P-site of the ribosome whenever there is an aminoacyl-tRNA in the A-site, but it takes several hours for new aminoacyl-tRNAs to enter the ribosome. These results are most likely to be the result of a highly defective form of which of the following proteins?
A) eIF-2.
B) eIF-2
C) eEF-1α
D) eEF-1βγ
E) eEF-2

Question

Quizplus · Accepted Answer

Each step of protein elongation comprises movement of the mRNA through the ribosome so that the tRNA carrying the elongating polypeptide resides within a pocket of the 60S subunit termed the P-site (for peptide site). The elongation factor eEF-1α carries each incoming aminoacyl-tRNA to the A-site (for amino acid site) dependent upon the correct codon-anticodon interactions. The peptide in the P-site is transferred to the amino acid in the A-site through the action of the ribozyme activity known as peptidyltransferase. The elongation factor eEF-2 induces translocation of the ribosome along the mRNA such that the naked tRNA is temporarily within the E-site (for ejection site) of the 60S ribosome and the peptidyl-tRNA is moved to the P-site leaving the A-site empty and residing over the next codon of the mRNA.

You Are Utilizing a Cell Culture System Derived from a Breast