Extracellular leucine-rich repeats

Onnerfjord P, Heathfield TF, Heinegard D. Identification of tyrosine sulfation in extracellular leucine-rich repeat proteins using mass spectrometry. J Biol Chem 2004 279 26-33. 

TLRs are transmembrane receptors comprising an extracellular leucine-rich repeat and a cytoplasmic Toll/interleukin-1 receptor (TIR) domain, which are connected through a transmembrane domain [4]. The TIR domain is structurally homologous... 

At least 12 ditferent TLRs have so far been identified in mammals (Uematsu and Akria 2007). TLRs are type I transmembrane PRRs that possess an extracellular domain contaiiung leucine-rich repeats (LRR), a transmembrane domain, and an... 

Hocking, A. M., Shinomura, T. and McQuillan, D. J. (1998). Leucine-rich repeat glycoproteins of the extracellular matrix. Matrix Biol. 17, 1-19. 

TLRs are type I transmembrane proteins that consist of three major domains (1) a leucine-rich repeat (LRR) extracellular domain, (2) a transmembrane domain, and (3) a cytoplasmic TIR domain. There are 10 human TLRs (TLRl-10) and 13 murine TLRs (TLRl-13, although TLRIO is not functional in mice because of a retroviral insertion) that each have a different PAMP specificity. TLRl-10 are conserved between humans and mice, but TLRll-13 are not present in humans. Thus, despite some... 

Leucine residues 2, 5, 7, 12, 20, and 24 of the motif are invariant in both type A and type B repeats of the ribonuclease inhibitor. An examination of more than 500 tandem repeats from 68 different proteins has shown that residues 20 and 24 can be other hydrophobic residues, whereas the remaining four leucine residues are present in all repeats. On the basis of the crystal structure of the ribonuclease inhibitor and the important structural role of these leucine residues, it has been possible to construct plausible structural models of several other proteins with leucine-rich motifs, such as the extracellular domains of the thyrotropin and gonadotropin receptors. 

The neurotrophins are unusual among polypeptide growth factors in that two different transmembrane proteins serve as receptors for each neurotrophin. The structural features of Trk tyrosine kinases and the p75 neurotrophin receptor are displayed in Fig. 1. The Trk subfamily of receptor tyrosine kinases is distinguished by immunoglobulin-C2 domains and repeats rich in leucine and cysteine residues in the extracellular domain and a tyrosine kinase domain with a small interruption and a short cytoplasmic tail. 

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