Final answer:
Peptide chain elongation in translation involves three G-protein family members, which are the elongation factors responsible for positioning the tRNA in the ribosome, translocation after peptide bond formation, and the release of deacylated tRNA.
Step-by-step explanation:
During the peptide chain elongation process in translation, there are three G-protein family members involved. These include the elongation factors that are essential for the entry and proper positioning of the aminoacyl-tRNA into the A site of the ribosome, for translocation of the tRNA from the A site to the P site after peptide bond formation, and for the exit of the uncharged tRNA from the E site.
Elongation factors such as EF-Tu (in bacteria) or eEF1A (in eukaryotes) are responsible for the delivery of the charged tRNA to the A site, accompanied by GTP hydrolysis. Another factor, EF-G (in bacteria) or eEF2 (in eukaryotes), is involved in translocating the peptidyl-tRNA from the A site to the P site. A third GTPase activity may be associated with the release of deacylated tRNA from the ribosome, although this is not always classified as an elongation factor. Thus, the correct answer to the question is C. Three.