The Bacterial Ribosome: A Programmed Enzyme

Abstract

Ribosome-dependent protein synthesis in bacteria represents a complex sequence of reactions involving more than 150 compounds. The ribosome, constructed from 53 individual proteins and 3 nucleic acids, functions as the enzyme which catalyzes peptide bond formation. In contrast to most known enzymes the ribosome is "programmed" by the mRNAthe short-lived transcript of DNA. The ribosome reads the nucleotide message of the mRNA and transforms its information into the amino acid sequence of a protein. In the course of this process, chemical bond energy is converted into directed mechanical motion. The model of protein biosynthesis on the programmable ribosome provides answers to the following questions: how is the mRNA framed into information units, how is the substrate specificity of the ribosome modulated by the codon of the mRNA, and how does the mRNA move with respect to the ribosome by one trinucleotide per peptide bond formed?