Amino acid requirement for the high affinity binding of a selected arginine-rich peptide with the HIV Rev-response element RNA.

The arginine-rich motif is a class of short arginine-rich peptides that bind to specific RNA structures that has been found to be a versatile framework for the design and selection of RNA-binding peptides. We previously identified novel peptides that bind to the Rev-response element (RRE) RNA of the HIV from an arginine-rich polypeptide library (ARPL) consisting of a polyarginine (15 mer) randomized at the N-terminal 10 positions. The selected peptides bound more strongly to the RRE than the natural binding partner, Rev, and contained glutamine residues that were assumed to be important for recognition of the G-A base pair. In addition, the peptides were predicted to bind to the RRE in an alpha-helical conformation. In this study, in order to understand the mechanism of the interaction between the RRE and the putative alpha-helical glutamine-containing peptides, the amino acid requirements for high affinity binding were analyzed by a combinatorial approach using a bacterial system for detecting RNA-peptide interactions. A consensus peptide, the DLA peptide, was elucidated, which consists of a single glutamine residue within a polyarginine context with the glutamine residue flanked at specific positions by three nonarginine residues, two of which appear to be important for alpha-helix stabilization. In addition, the DLA peptide was found to bind extremely tightly to the RRE with an affinity 50-fold higher than that of the Rev peptide as determined by a gel shift assay. A working model for the interaction of the DLA peptide to the RRE is proposed, which should aid in the development of peptide-based drugs that inhibit HIV replication, as well as in our understanding of polypeptide-RNA interactions.