Protein synthesis: Imprinting through molecular mimicry

The translation of genetic messages into proteins on ribosomes is catalyzed by a number of proteins that bind transiently to the ribosome [1,2]. These are the initiation, elongation and release (termination) factors. Several of these factors are GTP-hydrolyzing (G) proteins, which undergo a conformation transition between an active state with bound GTP and an inactive state with bound GDP. In bacteria, these translational GTPases are initiation factor 2 (IF-2), elongation factors Tu and G (EF-Tu and EF-G) and release factor 3 (RF-3). IF-2 and EF-Tu catalyze the binding of initiator and elongator tRNAs, respectively, to the ribosome, and RF-3 assists in the binding of RF-1 or RF-2. The latter two proteins have a relationship to tRNAs, as they recognize the stop codons of the mRNA. The three factors IF-2, EF-Tu and RF-3 thus have in common the property that they all catalyze the binding of tRNAs, or proteins with some tRNA-like properties, to the ribosome.