This repeat contains the conserved pattern CXCXC where X can be any amino acid. The repeat is found in up to five copies in Vascular endothelial growth factor C [2]. In the salivary glands of the dipteran Chironomus tentans, a specific messenger ribonucleoprotein (mRNP) particle, the Balbiani ring (BR) granule, can be visualised during its assembly on the gene and during its nucleocytoplasmic transport. This repeat is found over 70 copies in the balbiani ring protein 3 Swiss:Q03376. It is also found in some silk proteins [1].

1: Extraordinary conservation of cysteines among homologous Chironomus silk proteins sp185 and sp220. Case ST, Cox C, Bell WC, Hoffman RT, Martin J, Hamilton R; J Mol Evol 1997;44:452-462. PMID:9089085

2: A novel vascular endothelial growth factor, VEGF-C, is a ligand for the Flt4 (VEGFR-3) and KDR (VEGFR-2) receptor tyrosine kinases. Joukov V, Pajusola K, Kaipainen A, Chilov D, Lahtinen I, Kukk E, Saksela O, Kalkkinen N, Alitalo K; EMBO J 1996;15:290-298. PMID:8617204