Specific Interaction between RNA Phage Coat Proteins and RNA

This chapter describes the biochemistry of the interaction of phage coat protein with RNA and attempt to provide a molecular understanding of its high specificity. Coat protein binding is believed to serve two functions in the life cycle of the phage: 1) it acts as a translational repressor of the replicase gene early in infection, and 2) as an initiation site of phage assembly late in infection. This interaction has been extensively a prototype of sequence specific RNA-protein interactions. It is now clear that the phage coat proteins can be considered an example of a class of RNA hairpin binding proteins that are quite common in prokaryotes and eukaryotes. In case of bacteriophage coat protein, the coat protein assembles into phage-like capsids that can be purified by differential centrifugation and ion-exchange chromatography. Most coat proteins can be successfully renatured by the transfer from storage buffer directly into a variety of neutral buffers of moderate ionic strength. In many cases, these renatured proteins are fully active in both RNA binding and capsid assembly.