A cysteine rich repeat found in several different extracellular receptors. The function of the repeat is unknown. Three copies of the repeat are found Plexin (Swiss:P70206) [1]. Two copies of the repeat are found in mahogany protein. A related C. elegans protein (Swiss:Q19981) contains four copies of the repeat. The Met receptor contains a single copy of the repeat. The Pfam alignment shows 6 conserved cysteine residues that may form three conserved disulphide bridges, whereas [1] shows 8 conserved cysteines. The pattern of conservation suggests that cysteines 5 and 7 (that are not absolutely conserved) form a disulphide bridge (Personal observation. A Bateman).

1: Plexin: a novel neuronal cell surface molecule that mediates cell adhesion via a homophilic binding mechanism in the presence of calcium ions. Ohta K, Mizutani A, Kawakami A, Murakami Y, Kasuya Y, Takagi S, Tanaka H, Fujisawa H; Neuron 1995;14:1189-1199. PMID:7605632

2: Domains in plexins: links to integrins and transcription factors. Bork P, Doerks T, Springer TA, Snel B; Trends Biochem Sci 1999;24:261-263. PMID:10390613