Final answer:
EF-Tu is the G protein that complexes with GTP and aminoacyl-tRNA, aiding in delivering the tRNA to the A site of the ribosome during the elongation phase of protein synthesis in E. coli. The correct option is A.
Step-by-step explanation:
The G protein in question, which forms a complex with GTP and aminoacyl-tRNA to deliver it to the A site of the ribosome, is an important factor in the elongation phase of protein synthesis in E. coli. Within this process, the EF-Tu protein binds to aminoacyl-tRNA along with GTP to facilitate its entry into the A site of the ribosome.
After the aminoacyl-tRNA is placed, GTP is hydrolyzed, releasing EF-Tu to be recycled for another round of elongation. This protein is integral to the efficiency of translation, which allows E. coli to add amino acids to the growing polypeptide chain very rapidly.