THE DEAD-BOX PROTEIN DBPA INTERACTS SPECIFICALLY WITH THE PEPTIDYLTRANSFERASE CENTER IN 235-RIBOSOMAL-RNA

The Escherichia coli DEAD (Asp-Glu-Ala-Asp) box protein DbpA is a putative RNA helicase and established RNA-dependent ATPase and is the only member of the DEAD box protein family for which a specific RNA substrate, bacterial 23S rRNA, has been identified. We have investigated the nature of this specificity in depth and have localized by deletion mutagenesis and PCR a single region of 93 bases (bases 2496-2588) in 23S rRNA that is both necessary and sufficient for complete activation of ATPase activity df DbpA. This target region forms part of the peptidyltransferase center and includes many bases involved in interaction with the 3' terminal adenosines of both A- and P-site tRNAs. Deletion of stem loops within the 93-base segment abolished ATPase activation. Similarly, point mutations that disrupt babe pairing within stem structures ablated stimulation of ATPase activity. These data are consistent with roles for DbpA either in establishing and/or maintaining the correct three-dimensional structure of the peptidyltransferase center in 23S rRNA during ribosome assembly or in the peptidyltransferase reaction.