The HAS barrel is named after HerA-ATP Synthase. In ATP synthases, this domain is implicated in the assembly of the catalytic toroid and docking of accessory subunits, such as the subunit of the ATP synthase complex. Similar roles in docking of the functional partner, the NurA nuclease, and assembly of the HerA toroid complex appear likely for the HAS-barrel of the HerA family [1].

1: Comparative genomics of the FtsK-HerA superfamily of pumping ATPases: implications for the origins of chromosome segregation, cell division and viral capsid packaging. Iyer LM, Makarova KS, Koonin EV, Aravind L; Nucleic Acids Res. 2004;32:5260-5279. PMID:15466593