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.