Information on EC 5.6.2.7 - DEAD-box RNA helicase

RNA helicases, which participate in nearly all aspects of RNA metabolism, utilize the energy from ATP hydrolysis to unwind RNA. The engine core of helicases is usually made of a pair of RecA-like domains that form an NTP binding cleft at their interface. Changes in the chemical state of the NTP binding cleft (binding of the NTP or its hydrolysis products) alter the relative positions of the RecA-like domains and nucleic acid-binding domains, creating structural motions that disrupt the pairing of the nucleic acid, causing separation and unwinding. While most RNA helicases utilize a mechanism known as canonical duplex unwinding and translocate along the RNA (cf. EC 5.6.2.5, RNA 5′-3′ helicase and EC 5.6.2.6, RNA 3′-5′ helicase), DEAD-box RNA helicases differ by unwinding RNA via the local strand separation mechanism, which does not involve translocation. These helicases load directly on the duplex region, aided by single stranded or structured nucleic acid regions. Upon loading, the DEAD-box protein locally opens the duplex strands. This step requires binding of ATP, which is not hydrolysed. The local helix opening causes the remaining basepairs to dissociate without further action from the enzyme. Unwinding occurs without apparent polarity, and is limited to relatively short distances. ATP hydrolysis is required for release of the DEAD-box protein from the RNA. The name originates from the sequence D-E-A-D, which is found in Motif II of these proteins.