The Ocular Albinism Type 1 Gene Product is an N‐Glycoprotein but Glycosylation is not Required for its Subcellular Distribution

The ocular albinism type 1 (OA1) gene product is a membrane glycoprotein that may play a role in controlling melanosome growth and maturation. A number of mutations in the OA1 gene lead to ocular albinism due at least in part to retention of the aberrant protein in the endoplasmic reticulum. To examine whether N‐glycosylation plays a role in the post‐translational trafficking of the Oa1 protein, we constructed a series of mutant mouse Oa1 cDNAs encoding an Oa1‐green fluorescent protein fusion in which some or all of the potential glycosylation sites were eliminated by site‐directed mutagenesis. Biochemical studies in transfected cells treated with tunicamycin and peptide:N‐glycosidase F suggest that asparagine at amino acid 106 is essential for N‐glycosylation of the protein. Mutation at amino acid 106 that eliminated glycosylation did not affect the endo/lysosomal distribution of the Oa1 protein in either COS cells or cultured murine melanocytes.