Molecular Biology Commons^™

The coat proteins of the RNA bacteriophages Qβ and MS2 are specific RNA binding proteins. Although they possess common tertiary structures, they bind different RNA stem loops and thus provide useful models of specific protein-RNA recognition. Although the RNA-binding site of MS2 coat protein has been extensively characterized previously, little is known about Qβ. Here we describe the isolation of mutants that define the RNA-binding site of Qβ coat protein, showing that, as with MS2, it resides on the surface of a large β-sheet. Mutations are also described that convert Qβ coat protein to the RNA binding specificity of MS2. …

The coat proteins of RNA phages MS2 and GA are specific RNA-binding proteins which function to encapsidate viral RNA and to translationally repress synthesis of the viral replicase. The two proteins have highly homologous amino acid sequences, yet they show different RNA binding specificities, recognizing RNA stem-loop structures which differ primarily in the nucleotide sequences of their loops. We sought to convert MS2 coat protein to the RNA binding specificity of GA through the introduction of GA-like amino acid substitutions into the MS2 coat protein RNA-binding site. The effects of the mutations were determined by measuring the affinity of the …