Molecular characterization and genomic mapping of human IPM 200, a second member of a novel family of proteoglycans.

We report herein the characterization of the cDNA for a novel human chondroitin sulfate proteoglycan, designated IPM 200, and the chromosomal location of its gene, designated IMPG2. IPM 200 was isolated from the retinal interphotoreceptor matrix, a unique extracellular matrix that occupies the subretinal space between the apices of the retinal pigment epithelium and the neural retina. The cDNA contains an open reading frame of 3,726 bp that codes for a core protein with a deduced molecular weight of 138.5 kDa. The deduced IPM 200 core protein contains a putative transmembrane domain, two EGF-like repeats, numerous N- and O-linked glycosylation consensus sequences and one consensus sequence for glycosaminoglycan attachment. IMPG2 maps to human chromosome 3q12.2-12.3. Based on homologies within their amino acid sequences we propose that IPM 200 and a previously described human proteoglycan, IPM 150, form a new family of extracellular matrix glycoconjugates.