Zinc-finger antiviral protein (ZAP) is a host factor that specifically inhibits the replication of certain viruses, such as HIV-1, by targeting viral mRNA for degradation. This domain is a helix turn helix domain found at the N-terminal region constituting the top cockpit layer of the protein [1].

1: Structure of N-terminal domain of ZAP indicates how a zinc-finger protein recognizes complex RNA. Chen S, Xu Y, Zhang K, Wang X, Sun J, Gao G, Liu Y; Nat Struct Mol Biol. 2012;19:430-435. PMID:22407013