On the nomenclature of the IGF binding proteins

The insulin-like growth factor (IGF) I and II circulate in plasma complexed to carrier on binding proteins. On the basis of their chromatographically determined molecular size they have been designated 150–200 kD and 30–40 kD IGF binding proteins (BP). In recent years a growing number of proteins with IGF binding characteristics have been isolated from various body fluids, cell lines, and in various species. Provisional terminology based on source, species or molecular size has become increasingly confusing. Thus far three distinct binding proteins have been fully characterized and their amino acid sequence determined (1–9). During a workshop in the IGF binding proteins held in Vancouver, June 17–19, 1989, a proposal was put forward to adopt the designation 'IGFBP', with the addition of an arabic numeral and letter prefix to indicate species specificity as outlined in the following table. It should be stressed that until full amino acid nucleotide sequence data