The NHL repeat, named after NCL-1

CAPN3

Calpain-3 is a protein that in humans is encoded by the CAPN3 gene.-External links:* The MEROPS online database for peptidases and their inhibitors: ** LOVD mutation database:...

, HT2A

TRIM32

Tripartite motif-containing protein 32 is a protein that in humans is encoded by the TRIM32 gene. Since its discovery in 1995, TRIM32 has been shown to be implicated in a number of diverse biological pathways.- Structure :...

 and Lin-41, is an amino acid sequence found largely in a large number of eukaryotic

Eukaryote

A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

 and prokaryotic

Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

 protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s. For example, the repeat is found in a variety of enzymes of the copper type II, ascorbate-dependent monooxygenase

Copper type II ascorbate-dependent monooxygenase

In molecular biology, the copper type II ascorbate-dependent monooxygenases are a class of enzymes that require copper as a cofactor and which use ascorbate as an electron donor. This family contains two related enzymes, dopamine-beta-monooxygenase and peptidylglycine alpha-amidating monooxygenase...

 family which catalyse the C-terminus alpha-amidation of biological peptides. In many it occurs in tandem arrays, for example in the RING finger

RING finger domain

In molecular biology, a RING finger domain is a protein structural domain of zinc finger type which contains a Cys3HisCys4 amino acid motif which binds two zinc cations. This protein domain contains from 40 to 60 amino acids...

 beta-box, coiled-coil

Coiled coil

A coiled coil is a structural motif in proteins, in which 2-7 alpha-helices are coiled together like the strands of a rope . Many coiled coil type proteins are involved in important biological functions such as the regulation of gene expression e.g. transcription factors...

(RBCC) eukaryotic growth regulators. The 'Brain Tumor' protein (Brat) is one such growth regulator that contains a 6-bladed NHL-repeat beta-propeller.

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.