InterPro domain: IPR001258

The NHL repeat, named after NCL-1, HT2A andLin-41, is found largely in a large number of eukaryotic and prokaryotic proteins. For example, the repeat is found in a variety of enzymes of the copper type II, ascorbate-dependent monooxygenase family which catalyse the C terminus alpha-amidation of biological peptides [ 1 ].In many it occurs in tandem arrays, for example in the ringfinger beta-box, coiled-coil (RBCC) eukaryotic growth regulators [ 2 ]. The 'Brain Tumor' protein (Brat) is one such growth regulator that contains a 6-bladed NHL-repeat beta-propeller [ 3 , 4 ].

The NHL repeats are also found in serine/threonine protein kinase (STPK) in diverse range of pathogenic bacteria. These STPK are transmembrane receptors with a intracellular N-terminal kinase domain and extracellular C-terminal sensor domain. In the STPK, PknD, from Mycobacterium tuberculosis, the sensor domain forms a rigid, six-bladed b-propeller composed of NHL repeats with a flexible tether to the transmembrane domain.

1. The membrane-bound bifunctional peptidylglycine alpha-amidating monooxygenase protein. Exploration of its domain structure through limited proteolysis. J. Biol. Chem. 266, 17004-10
2. A novel repeat domain that is often associated with RING finger and B-box motifs. Trends Biochem. Sci. 23, 474-5
3. Model of the brain tumor-Pumilio translation repressor complex. Genes Dev. 17, 2508-13
4. Structure of Pumilio reveals similarity between RNA and peptide binding motifs. Cell 105, 281-9