<p>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 [<cite idref="PUB00002654"/>].In many it occurs in tandem arrays, for example in the ringfinger beta-box, coiled-coil (RBCC) eukaryotic growth regulators [<cite idref="PUB00005488"/>]. The 'Brain Tumor' protein (Brat) is one such growth regulator that contains a 6-bladed NHL-repeat beta-propeller [<cite idref="PUB00017037"/>, <cite idref="PUB00020208"/>]. </p><p>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 <taxon tax_id="1773">Mycobacterium tuberculosis</taxon>, the sensor domain forms a rigid, six-bladed b-propeller composed of NHL repeats with a flexible tether to the transmembrane domain.</p> NHL repeat