Reptilian MPR 300 is also the IGF-IIR: Cloning, sequencing and functional characterization of the IGF-II binding domain

The mammalian cation-independent mannose 6-phosphate/insulin-like growth factor (IGF)-II receptor binds IGF-II with high affinity. Ligands transported by the MPR 300/IGF-IIR include IGF-II and mannose 6-phosphate-modified proteins. By targeting IGF-II to lysosomal degradation, it plays a key role in the maintenance of correct IGF-II levels in the circulation and in target tissues. Although, from our studies we found homologous receptor in calotes but its functional significance was not known. We present here the first report on the calotes MPR 300/IGF-IIR binds IGF-II with K_d of 12.02 nM; these findings provide new and strong evidence that MPR 300/IGF-IIR in Calotes versicolor binds IGFII with high affinity.