Interphotoreceptor Matrix Proteoglycan 1 (IMPG1)

Interphotoreceptor matrix glycoconjugates, which are largely proteoglycans, appear to participate in retinal adhesion and in maintaining photoreceptor viability. Kuehn and Hageman (1995) isolated monkey interphotoreceptor matrix proteoglycan-1 (Impg1), which the authors designated IPM-150, from an SDS-polyacrylamide gel and utilized amino acid sequence data from the isolated protein to design RT-PCR primers for amplification of monkey retinal mRNA. They used the resulting clone to screen a human cDNA library and isolated an 809-bp cDNA, which shares 97% homology with the monkey sequence and encodes human IMPG1. The putative protein, a chondroitin 6-sulfate proteoglycan, contains 4 consensus sequences for hyaluronan binding and 3 for N-glycosylation, as well as several potential O-glycosylation sites.