The helicase associated domain (HA2) has an all alpha-helical fold and consists of a N-terminal winged-helix (WH) domain (Pfam:PF04408) and a C-terminal degenerate helical-bundle domain, referred to as the ratchet-like domain [1,2,3]. These domains collaborate with the RecA domains at the N-terminal in completing an RNA binding channel to allow the helicases to keep a stable grip on the RNA [3]. This entry represents the ratchet-like domain, which may be important for RNA translocation [1,2].

1: Structure of the RNA Helicase MLE Reveals the Molecular Mechanisms for Uridine Specificity and RNA-ATP Coupling. Prabu JR, Muller M, Thomae AW, Schussler S, Bonneau F, Becker PB, Conti E; Mol Cell. 2015;60:487-499. PMID:26545078

2: Structural and functional characterisation of human RNA helicase DHX8 provides insights into the mechanism of RNA-stimulated ADP release. Felisberto-Rodrigues C, Thomas JC, McAndrew C, Le Bihan YV, Burke R, Workman P, van Montfort RLM; Biochem J. 2019;476:2521-2543. PMID:31409651

3: Structural basis for DEAH-helicase activation by G-patch proteins. Studer MK, Ivanovic L, Weber ME, Marti S, Jonas S; Proc Natl Acad Sci U S A. 2020;117:7159-7170. PMID:32179686