The NHL(NCL-1, HT2A and LIN-41)-repeat is found in multiple tandem copies, typically as 6 instances. It is about 40 residues long and resembles the WD repeat and other beta-propeller structures. The repeats have a catalytic activity in Peptidyl-glycine alpha-amidating monooxygenase; proteolysis has shown that the Peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL) activity is localized to the repeats. Tripartite motif-containing protein 32 interacts with the activation domain of Tat. This interaction is mediated by the NHL repeats.
Jiyao W et al.(2023). "The conserved domain database in 2023.",