DISSECTING RNA-PROTEIN INTERACTIONS - RNA-RNA RECOGNITION BY ROP

The ColE1 plasmid of E. coli encodes a small RNA-binding protein, Rop, which is involved in the regulation of plasmid copy number, Rop, a 4- helix bundle protein, facilitates sense-antisense RNA pairing by bindi ng to the transiently formed hairpin pairs of RNA I and the complement ary RNA II. We have identified the residues of Rop that are involved i n RNA recognition. The residues form a narrow stripe down one face of the bundle and are symmetrically arranged, with recognition centered a bout two phenylalanine residues. Our results suggest that these phenyl alanine residues interact with the loop region of the hairpin pair, wi th additional interactions between eight polar residues and the phosph ate backbone. By modifying the identity of residue 14, we have created a variant of Rop that displays altered RNA binding specificity. The r esults of our studies allow us to present a detailed picture of RNA-pr otein recognition in a novel model system.