Replacement of Ribosomal Protein S1 by Interference Factor iα in Ribosomal Binding of Phage MS2 RNA

The MS2 RNA binding capacity of 30S ribosomal subunits, which is lost when protein S1 is removed, can be restored following incubation with interference factor iα and repelleting. Polyacrylamide-agarose gel electrophoresis shows that, under these conditions, a faster moving, non-RNA binding 30S species, which contains no S1, is converted to a slower moving RNA-binding one, having the same mobility as the 30S species that contains protein S1. Factor iα binds to single-stranded RNAs in a pattern that closely resembles the RNA binding pattern of initiation factor IF-3.