Insulin-like growth factor binding proteins: a proposed superfamily.
The conventional concept is that the insulin-like growth factor binding proteins (IGFBPs) are cysteine-rich proteins, with conserved N- and C-domains, that are capable of binding insulin-like growth factors (IGFs) with high affinity. This dogma was recently challenged by the discovery of a group of cysteine-rich proteins that share important structural similarities with the IGFBPs, but have demonstrably lower affinity for IGFs. It is therefore proposed that these IGFBP-related proteins (IGFBP-rPs) and the IGFBPs constitute an IGFBP superfamily. We speculate that the IGFBP superfamily is derived from an ancestral gene/protein that was critically involved in the regulation of cell growth and was capable of binding IGF peptides. Over the course of evolution, some members (IGFBPs) evolved into high-affinity IGF binders and others (IGFBP-rPs) into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means.
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Department of Pediatrics, Oregon Health Sciences University, Portland 97202, USA.
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D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D015870:Gene Expression; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000502:physiology; D012680:Sensitivity and Specificity; D013329:Structure-Activity Relationship
D018969:Insulin-Like Growth Factor Binding Proteins