| CREG binds to the cation independent mannose 6 phosphate ( M6P ) / insulin like growth factor 2 ( IGF 2 ) receptor ( IGF2R ) ( M6P / IGF2R ) , and this receptor has been shown to be required for CREG induced growth suppression . ^^^ Thus , dimerization of glycosylated CREG likely presents a bivalent ligand for the M6P / IGF2R . ^^^ A mutant of CREG lacking a part of this loop maintained overall structure and dimerization , as well as M6P / IGF2R binding , but lost the growth suppression activity of WT CREG . ^^^ Thus , analysis of a structure based mutant of CREG revealed that binding to M6P / IGF2R , while necessary , is not sufficient for CREG induced growth suppression . ^^^ |