Polypeptide synthesis, bond, chain, initiation, elongation

Initiation factors contribute to the ribosome complex with the messenger RNA and the initiator methionyl-tRNA. Elongation factors assist the binding of all the other tRNAs and the translocation reaction that must occur after each peptide bond is made. Termination factors recognize a stop signal and lead to the termination of polypeptide synthesis and the release of the polypeptide chain and the messenger from the ribosome. 

The mechanism whereby RNA is translated into protein is complex, and the cell devotes considerable resources to the translational machinery. The components include 20 different amino acids, transfer RNAs, aminoacyl-tRNA synthetases, ribosomes, and a number of protein factors which cycle on and off the ribosomes and facilitate various steps in initiation of translation, elongation of the nascent polypeptide chain, and termination of synthesis with release of the completed polypeptide from the ribosome. The process depends on a supply of energy provided by ATP and GTP. The rate of protein synthesis is typically in the range of 6 (immature red blood cells of the rabbit) to 20 Escherichia coli growing optimally) peptide bonds per sec. at 37°C. 

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