The Escherichia coli DEAD protein DbpA is an
RNA-specific ATPase that is activated by a 153-nt fragment
within domain V of 23S rRNA. A series of RNA subfragments
and sequence changes were used to identify the recognition
elements of this RNA–protein interaction. Reducing
the size of the fully active 153-nt RNA yields compromised
substrates in which both RNA and ATP binding are weakened
considerably without affecting the maximal rate of ATP
hydrolysis. All RNAs that stimulate ATPase activity contain
hairpin 92 of 23S rRNA, which is known to interact with
the 3′ end of tRNAs in the ribosomal A-site. RNAs
with base mutations within this hairpin fail to activate
ATP hydrolysis, suggesting that it is a critical recognition
element for DbpA. Although the isolated hairpin fails to
activate DbpA, RNAs with an extension of approximately
15 nt on either the 5′ or 3′ side of hairpin
92 elicit full ATPase activity. These results suggest that
the binding of DbpA to RNA requires sequence-specific interactions
with hairpin 92 as well as nonspecific interactions with
the RNA extension. A model relating the RNA binding and
ATPase activities of DbpA is presented.